There's a good video on this: http://www.webfaction.com/screencasts/trac-svn/trac-svn-screencast.html

But if you'd like to skip the video, after you've installed the application, here are the steps:

Add users using the htpasswd command

Remove anonymous permissions

trac-admin . permission list

Remove these permissions from anonymous, then add them to mcombs:

MILESTONE_CREATE, MILESTONE_DELETE, MILESTONE_MODIFY

REPORT_CREATE, REPORT_DELETE, REPORT_MODIFY

TICKET_CREATE, TICKET_MODIFY

WIKI-CREATE, WIKI_DELETE, WIKI_MODIFY

trac-admin . permission remove anonymous XXX

trac-admin . permission add mcombs XXX