I have some rooms I want to add to a dungeon (to make it render properly) and I can't figure out exactly what the process is for adding rooms and joining the room to an existing one with portals. Can someone tell me exactly what to do, or (even better) guide me to a video tutorial? I can't figure this one out.

You need to think with portals.

No really... portals are used to connect rooms. There's a Bethesda video tutorial on doing just that.

http://www.youtube.com/watch?v=acfuZiQh83Y

Thanks, that's exactly what I was hoping for.