The admin can post right away. Bloggers need to register to your site. The admin gets a mail and needs to ferify this.
At least that's the standard situation. You can change this behaviour.

Good luck

can you walk me through how to get rid of the activation step??

No and yes. I give you this [url=http://www.fralenuvol.com/albero/servizi/webmaster/scripts/b2evolution_autoblog_plugin.php]link to the autoblog plugin[/url] instead. Do seach the forum on this plugin and you will discover many tips and tricks.

Good luck