The class is very simple. You simply need to call it and it will generate a dropdown functionality on all marked ULs.
It assumes each li has exactly one anchor in it. Sub-menues are neted ULs with specified class (default to submenu).
NOTE: You can use whatever structure you would like, but you should note that the keyboard accessiblility assumes each menu item has an anchor in it. I haven't tested it, but a missing anchor might break the class
For more documentation, go here