this is done through your module manager.
What you have to do is go through each of your modules and manually select which menu items you want.
So to get only a header for your forum. Go into your module manager and click on each published module, then on the right side you will see a list of all your menu items.
By default it has all of the menu items set to display the module, To deselect one menu item you would think all you would have to do is click on the menu items that you want to display, but when you try to click on the menu items you will see that it does not select both….there is a little trick that wasn’t obvious to me until I was shown.
The trick to get it so that, for example, the forum does not show the module, you have to click on the top most menu item then hold your shift key down while you click on the bottom most menu item. This will select all items. Then hold control key while you click on any item in that list to deselect it. When you are done click Save.
Go through all your modules (I believe its all of them except the main menu, but you can test and figure it from there) and deselect the forum