Doing navigation in Windows 8 apps is a little confusing and not well documented. With that in mind, I put together a sample which should help clarify things.
Joe Stegman outlines the basics in this forum response but let me drill in a bit. The confusing bit is that the templates in VS make your pages use UserControl as the root instead of Page. So, you have to manually change the root element to Page. The other confusing bit is that you need to handle things in the OnNavigatedTo override. That's how you can get the NavigationEventArgs and get at parameters that you've passed.
Beware of putting any logic into the Page_Loaded event when using Navigation. I hit a really weird bug where my i/o calls were mysteriously failing when I tried to do them in the Loaded event after I'd committed to the Page navigation paradigm.