drop-down menus

I would like a drop-down menu from one item on the nav bar, to list the pages under that parent page.
In Theme Options, there’s a check-off box for “Enable slide and fade effects for drop-down menus,” suggesting that drop-down menus should exist. How do I get one?
I have found where I can create the menu in Menus. But I don’t see how to make this menu appear on the site. At Menus, it also says “Your theme supports 1 menu. Select which menu you would like to use.” That suggests that I can only have 1 menu, the one appearing in the nav bar, and that no drop-down menu could exist.