Joomla Templates - Category Drop-Down Menu in Jbusiness template

I have just purchased the J business template but am having problems of signing elements to the modules. The installation guide is next to useless, it tells you how to create menus etc, but it doesn't actually cover the actual template itself. For instance, I'm trying to assign categories to the drop-down as demonstrated in the demo template, however it doesn't seem to work, I just end up with a menu of all the categories,