Primary Links drop-down menu doesn't work as default

Hi,
I see that drop-down menus from the primary menu don't work as default with Drupify. I've been trying to find a work-around and played a bit with Nice Menus, but this just adds a new menu, when I want a drop-down from the existing primary menu (the greeen bar across the top of the page). Could anyone help me out? I find drop-downs are essential for intuitive and efficient site browsing, so if I can't get this to work, I will have to change theme completely!
Cheers