MyBB Community Forums

I'm a total noob with myBB and everything, managed to set up a forum, threw like 40 plugins in - tried to register as a new user, but for some reason can't figure out how to do I post a new Thread as a regular user? http://forum.scatt.com/ here is the forum 

Also, if anyone could help - how do I arrange threads into different categories on the frontpage (like MyBB community has it with "1.8 support", @Development", "Resources" etc)?

Go to the ACP (Administration Control Panel) and when logged in, go to "Forum & Posts", you'll be on the Forum Management page where you can add Categories, Forums and Sub-Forums.

And to post threads... When logged as user (simple member or admin) and in a forum page (http://forum.scatt.com/forum-2.html as example), you may have a button somewhere "Post thread".