http://manual.b2evolution.net/Css_files

I bookmarked that page, thanks. I did try to put a line or two in the custom.css file, but it didn't just change my text, it changed the text that inside of every post as well (i.e., permalink, post title, etc.), and that is not what I want to do. If I make my text smaller, then those other things become unreadable.

Is it not possible to change certain text inside of a post?

what is the url to your blog? and bookmarking isnt useful, reading is. nudge nudge wink wink...

.AUSR. Musings
http://studioreflections.com/ausrmusings/

the text within your posts is controlled here, within custom.css:

bText {
margin-top: 0px;
margin-bottom: 0px;
}

so for instance,

bText {
font-size:20px;
font-family: Arial,Verdana,georgia,sans-serif;
margin-top: 0px;
margin-bottom: 0px;
}

would change the font size and family

...thank-you.