I came across a general help page that describes how to use the forum from the ground up. It's quite good, in that it describes most things in detail, but it's also quite long as a result. If you're stuck, it's well worth a read. Otherwise, just try some things and see what works.
Note that this is generic documentation for this bulletin board software. There may be a few differences in this installation. In particular the user profile details may look a bit different, but the fundamentals are the same. Karma is also not enabled.
A basic forum help page for beginners