This is exactly what I've been trying to do as well.
I couldn't figure out what Mary was talking about editing the Topic Outline (I'm on Moodle 1.9.3), but I'm going to explore themes now.
I added a Community Forum somehow to the main Moodle entry page for my site, but I'm not sure where that forum is held (other than on the main page). It's more of a new forum I think, and is only on the main page, instead of acessible from each course.