Re: hide subforums on main page
When you go into a forum, it should show you all the sub-forums available. If there are no topics in that forum however, it may just immediately jump to add new topic – that may be a bug in how bbPress works. Try creating a test topic in the main forum that has sub-forums.
If your forum has topics and still does not show sub-forums, you edited your theme somewhere and removed it or you are using a theme that removed the feature. If so, put into pastebin your forum.php page from your theme and show it to me.