Trying to use Cascading Nav


Hello, I am trying to use cascadig nav ina a WSS3 site.
I deployed the package for my site.
I created the list with all the columns.
I added the web part inside a page but I see just a normal list instead of the working cascading nav menu. Where is the mistake?
One mor information: I can add the web part but in the Site features I don't see the it for the activation/deactivation.
It is a great idea to work about a cascading nav menu, because most customers ask for it for web sites.
Thank you very much.