Below is a sample messages.po file for french so you can get an idea.

Of course you could edit this with a plain text editor, but your life will be much easier if you use a GUI tool like poedit !

# b2evolution - French language file
# Copyright (C) 2003 François PLANQUE
# This file is distributed under the same license as the b2evolution package.
# François PLANQUE <http://fplanque.net>, 2003
#
msgid ""
msgstr ""
"Project-Id-Version: b2evolution 0.8.3-alpha1\n"
"POT-Creation-Date: 2003-08-08 16:33+0200\n"
"PO-Revision-Date: 2003-08-08 17:10+0100\n"
"Last-Translator: François PLANQUE <http://fplanque.net/>\n"
"Language-Team: François PLANQUE <http://fplanque.net/>\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=iso-8859-1\n"
"Content-Transfer-Encoding: 8bit\n"

#: ..\..\..\noskin_a.php:315
#: ..\..\..\noskin_all.php:317
#: ..\..\..\noskin_b.php:316
#: ..\..\..\noskin_roll.php:315
#: ..\..\..\skins\babyblues\_main.php:103
#: ..\..\..\skins\bluesky\_main.php:222
#: ..\..\..\skins\custom\_main.php:260
#: ..\..\..\skins\fplanque2002\_main.php:289
#: ..\..\..\skins\guadeloupe\_main.php:222
#: ..\..\..\skins\originalb2\_main.php:159
#, php-format
msgid "Totals: %d posts - %d queries - %01.3f seconds"
msgstr "Totaux: %d articles - %d requêtes - %01.3f secondes"

#: ..\..\..\admin\b2edit.php:55
msgid "New post in blog:"
msgstr "Poster dans le blog:"

#: ..\..\..\admin\b2edit.php:100
msgid "Editing post"
msgstr "Edition d'un article"

#: ..\..\..\admin\b2edit.php:145
msgid "Editing comment"
msgstr "Edition d'un commentaire"

#: ..\..\..\admin\b2edit.php:175
msgid "Browse blog:"
msgstr "Parcourir le blog:"

#: ..\..\..\b2evocore\_class_pop3.php:80
#: ..\..\..\b2evocore\_class_pop3.php:88
#: ..\..\..\b2evocore\_class_pop3.php:100
msgid "POP3 connect:"
msgstr "POP3 connect:"

#: ..\..\..\b2evocore\_class_pop3.php:80
msgid "No server specified"
msgstr "Pas de serveur spécifié"

#: ..\..\..\b2evocore\_class_pop3.php:88
#: ..\..\..\b2evocore\_class_pop3.php:100
#: ..\..\..\b2evocore\_class_pop3.php:139
#: ..\..\..\b2evocore\_class_pop3.php:274
#: ..\..\..\b2evocore\_class_pop3.php:328
#: ..\..\..\b2evocore\_class_pop3.php:339
#: ..\..\..\b2evocore\_class_pop3.php:387
#: ..\..\..\b2evocore\_class_pop3.php:420
#: ..\..\..\b2evocore\_class_pop3.php:453
#: ..\..\..\b2evocore\_class_pop3.php:552
#: ..\..\..\b2evocore\_class_pop3.php:575
msgid "Error "
msgstr "Erreur"

#: ..\..\..\b2evocore\_class_pop3.php:108
#, fuzzy
msgid "POP3: premature NOOP OK, NOT an RFC 1939 Compliant server"
msgstr "POP3: premature NOOP OK, le serveur n'est pas conforme à la RFC 1939"

#: ..\..\..\b2evocore\_class_pop3.php:118
msgid "POP3 noop:"
msgstr "POP3 noop:"

#: ..\..\..\b2evocore\_class_pop3.php:118
#: ..\..\..\b2evocore\_class_pop3.php:184
#: ..\..\..\b2evocore\_class_pop3.php:233
#: ..\..\..\b2evocore\_class_pop3.php:258
#: ..\..\..\b2evocore\_class_pop3.php:300
#: ..\..\..\b2evocore\_class_pop3.php:374
#: ..\..\..\b2evocore\_class_pop3.php:413
#: ..\..\..\b2evocore\_class_pop3.php:443
#: ..\..\..\b2evocore\_class_pop3.php:477
#: ..\..\..\b2evocore\_class_pop3.php:540
#: ..\..\..\b2evocore\_class_pop3.php:608
msgid "No connection to server"
msgstr "Pas de connexion au serveur"

#: ..\..\..\b2evocore\_class_pop3.php:131
#: ..\..\..\b2evocore\_class_pop3.php:134
#: ..\..\..\b2evocore\_class_pop3.php:139
msgid "POP3 user:"
msgstr "POP3 user:"

#: ..\..\..\b2evocore\_class_pop3.php:131
#: ..\..\..\b2evocore\_class_pop3.php:190
msgid "No login ID submitted"
msgstr "Aucun identifiant n'a été soumis"

#: ..\..\..\b2evocore\_class_pop3.php:134
#: ..\..\..\b2evocore\_class_pop3.php:154
msgid "connection not established"
msgstr "connexion non établie"

#: ..\..\..\b2evocore\_class_pop3.php:151
#: ..\..\..\b2evocore\_class_pop3.php:154
#: ..\..\..\b2evocore\_class_pop3.php:159
#: ..\..\..\b2evocore\_class_pop3.php:168
msgid "POP3 pass:"
msgstr "POP3 pass:"

#: ..\..\..\b2evocore\_class_pop3.php:151
#: ..\..\..\b2evocore\_class_pop3.php:193
msgid "No password submitted"
msgstr "Aucun mot de passe n'a été soumis"

#: ..\..\..\b2evocore\_class_pop3.php:159
msgid "authentication failed "
msgstr "l'autentification a échoué"

#: ..\..\..\b2evocore\_class_pop3.php:168
#: ..\..\..\b2evocore\_class_pop3.php:217
msgid "NOOP failed. Server not RFC 1939 compliant"
msgstr "NOOP à échoué. Le serveur n'est pas conforme à la RFC 1939"

#: ..\..\..\b2evocore\_class_pop3.php:184
#: ..\..\..\b2evocore\_class_pop3.php:190
#: ..\..\..\b2evocore\_class_pop3.php:193
#: ..\..\..\b2evocore\_class_pop3.php:198
#: ..\..\..\b2evocore\_class_pop3.php:208
#: ..\..\..\b2evocore\_class_pop3.php:217
msgid "POP3 apop:"
msgstr "POP3 apop:"

#: ..\..\..\b2evocore\_class_pop3.php:198
#, fuzzy
msgid "No server banner"
msgstr "No server banner"

#: ..\..\..\b2evocore\_class_pop3.php:198
#: ..\..\..\b2evocore\_class_pop3.php:208
msgid "abort"
msgstr "abandon"

#: ..\..\..\b2evocore\_class_pop3.php:208
msgid "apop authentication failed"
msgstr "l'authentification apop a échoué"

#: ..\..\..\b2evocore\_class_pop3.php:233
msgid "POP3 login:"
msgstr "POP3 login:"

#: ..\..\..\b2evocore\_class_pop3.php:258
#: ..\..\..\b2evocore\_class_pop3.php:274
msgid "POP3 top:"
msgstr "POP3 top:"

#: ..\..\..\b2evocore\_class_pop3.php:300
#: ..\..\..\b2evocore\_class_pop3.php:328
#: ..\..\..\b2evocore\_class_pop3.php:339
#: ..\..\..\b2evocore\_class_pop3.php:351
msgid "POP3 pop_list:"
msgstr "POP3 pop_list:"

#: ..\..\..\b2evocore\_class_pop3.php:351
msgid "Premature end of list"
msgstr "Fin de liste prématurée"

#: ..\..\..\b2evocore\_class_pop3.php:374
#: ..\..\..\b2evocore\_class_pop3.php:387
msgid "POP3 get:"
msgstr "POP3 get:"

#: ..\..\..\b2evocore\_class_pop3.php:413
#: ..\..\..\b2evocore\_class_pop3.php:420
msgid "POP3 last:"
msgstr "POP3 last:"

#: ..\..\..\b2evocore\_class_pop3.php:443
#: ..\..\..\b2evocore\_class_pop3.php:453
msgid "POP3 reset:"
msgstr "POP3 reset:"

#: ..\..\..\b2evocore\_class_pop3.php:477
#: ..\..\..\b2evocore\_class_pop3.php:483
msgid "POP3 send_cmd:"
msgstr "POP3 send_cmd:"

#: ..\..\..\b2evocore\_class_pop3.php:483
msgid "Empty command string"
msgstr "Chaîne de commande vide"

#: ..\..\..\b2evocore\_class_pop3.php:503
msgid "POP3 quit:"
msgstr "POP3 quit:"

#: ..\..\..\b2evocore\_class_pop3.php:503
msgid "connection does not exist"
msgstr "la connexion n'existe pas"

#: ..\..\..\b2evocore\_class_pop3.php:540
#: ..\..\..\b2evocore\_class_pop3.php:552
#: ..\..\..\b2evocore\_class_pop3.php:575
msgid "POP3 uidl:"
msgstr "POP3 uidl:"

#: ..\..\..\b2evocore\_class_pop3.php:608
#: ..\..\..\b2evocore\_class_pop3.php:613
#: ..\..\..\b2evocore\_class_pop3.php:619
msgid "POP3 delete:"
msgstr "POP3 delete:"

#: ..\..\..\b2evocore\_class_pop3.php:613
msgid "No msg number submitted"
msgstr "Aucun numéro de message n'a été soumis"

#: ..\..\..\b2evocore\_class_pop3.php:619
msgid "Command failed "
msgstr "La commande a échoué"

#. TRANS: Link to comments for current post
#: ..\..\..\b2evocore\_edit_showposts.php:113
msgid "no comment"
msgstr "pas de commentaire"

#: ..\..\..\b2evocore\_edit_showposts.php:113
#: ..\..\..\b2evocore\_functions_trackback.php:153
msgid "1 comment"
msgstr "1 commentaire"

#: ..\..\..\b2evocore\_edit_showposts.php:113
#: ..\..\..\b2evocore\_functions_trackback.php:154
#, php-format
msgid "% comments"
msgstr "% commentaires"

#: ..\..\..\b2evocore\_edit_showposts.php:114
msgid ", 1 TrackBack"
msgstr ", 1 TrackBack"

#: ..\..\..\b2evocore\_edit_showposts.php:114
msgid ", % TrackBacks"
msgstr ", % TrackBacks"

#. TRANS: When the categories for a specific post are displayed, the user can click
#. on these cats to browse them, this is the default href title displayed there
#: ..\..\..\b2evocore\_functions_cats.php:611
msgid "Browse category"
msgstr "Afficher cette catégorie"

#: ..\..\..\b2evocore\_functions_comments.php:149
msgid "TrackBack (0)"
msgstr "TrackBack (0)"

#: ..\..\..\b2evocore\_functions_comments.php:150
msgid "TrackBack (1)"
msgstr "TrackBack (1)"

#: ..\..\..\b2evocore\_functions_comments.php:151
msgid "TrackBacks (%)"
msgstr "TrackBacks (%)"

#: ..\..\..\b2evocore\_functions_trackback.php:152
msgid "Leave a comment..."
msgstr "Laisser un commentaire..."

#: ..\..\..\b2evocore\_menutop.php:103
msgid "New Post"
msgstr "Poster"

#: ..\..\..\b2evocore\_menutop.php:105
msgid "Browse/Edit"
msgstr "Parcourir"

#: ..\..\..\b2evocore\_menutop.php:125
msgid "Users"
msgstr "Utilisateurs"

#: ..\..\..\b2evocore\_menutop.php:127
msgid "My Profile"
msgstr "Mon Profil"

#: ..\..\..\b2evocore\_menutop.php:132
msgid "Exit to blogs"
msgstr "Retour aux blogs"

#: ..\..\..\b2evocore\_menutop.php:134
msgid "Logout"
msgstr "Déconnexion"

#: ..\..\..\conf\b2evo_locale.php:53
msgid "Sunday"
msgstr "Dimanche"

#: ..\..\..\conf\b2evo_locale.php:54
msgid "Monday"
msgstr "Lundi"

#: ..\..\..\conf\b2evo_locale.php:55
msgid "Tuesday"
msgstr "Mardi"

#: ..\..\..\conf\b2evo_locale.php:56
msgid "Wednesday"
msgstr "Mercredi"

#: ..\..\..\conf\b2evo_locale.php:57
msgid "Thursday"
msgstr "Jeudi"

#: ..\..\..\conf\b2evo_locale.php:58
msgid "Friday"
msgstr "Vendredi"

#: ..\..\..\conf\b2evo_locale.php:59
msgid "Saturday"
msgstr "Samedi"

#: ..\..\..\conf\b2evo_locale.php:62
msgid "January"
msgstr "Janvier"

#: ..\..\..\conf\b2evo_locale.php:63
msgid "February"
msgstr "Février"

#: ..\..\..\conf\b2evo_locale.php:64
msgid "March"
msgstr "Mars"

#: ..\..\..\conf\b2evo_locale.php:65
msgid "April"
msgstr "Avril"

#: ..\..\..\conf\b2evo_locale.php:66
msgid "May"
msgstr "Mai"

#: ..\..\..\conf\b2evo_locale.php:67
msgid "June"
msgstr "Juin"

#: ..\..\..\conf\b2evo_locale.php:68
msgid "July"
msgstr "Juillet"

#: ..\..\..\conf\b2evo_locale.php:69
msgid "August"
msgstr "Août"

#: ..\..\..\conf\b2evo_locale.php:70
msgid "September"
msgstr "Septembre"

#: ..\..\..\conf\b2evo_locale.php:71
msgid "October"
msgstr "Octobre"

#: ..\..\..\conf\b2evo_locale.php:72
msgid "November"
msgstr "Novembre"

#: ..\..\..\conf\b2evo_locale.php:73
msgid "December"
msgstr "Décembre"

#: ..\..\..\skins\fplanque2002\_main.php:105
msgid ", Categories: "
msgstr ", Catégories: "