Trac administration with real examples
Run trac-admin commands on the server hosting the trac sites. In our Debian server setup at least, individual projects are in the /srv/trac/ directory, and every trac-admin command should be followed by the path to the project you care about.
For more information than man will give you, use:
To make a user an admin (I believe this will automatically create a new user if it has to) --
trac-admin /srv/trac/example permission add username TRAC_ADMIN
NOTE: You may have to run these commands with sudo, that is,
sudo trac-admin /srv/trac/example permission add username TRAC_ADMIN in the above case.
TRAC_ADMIN is a really useful permission because once you give it to yourself you can do everything else through Trac's user interface! Where, as Stefan wrote, "The (web) admin section of trac can be reached by clicking the admin button to the right in the navigation bar. There you can manipulate milestones, components, permissions etc."
To see what permissions are available (and what all users have), use:
trac-admin /srv/trac/example permission list
And for a specific user:
trac-admin /srv/trac/example permission list username