See the article about using Superfish in mojoPortal, if you follow those instructions correctly it should work. We have example skins such as the jqueryui skin that uses Superfish.
For the example you are trying to do it seems to require different css, you need to download their css file superfish-navbar.css, put it in your skin folder and add it in the style.config file below the stylemeu.css that has the main superfish css.
Hope that helps,
Joe