Hi,
To install the add on products is very similar to installing mojoPortal. The package has a wwwroot folder, you copy the contents of that folder into the root of your mojoPortal installation, then you visit the /Setup/Default.aspx page to complete the installation.
Once installed you add it to pages the same as any other feature in mojoPortal, by clicking the "Edit this Page" link to get to PageLayout.aspx, the dropdown list of features on that page will include the newly installed product(s) and you can add it to the page just like any of the included free features that come with mojoPortal.
You can try out the add on products and create test pages with them on our demo site.
Hope that helps,
Joe