How Do I Video Create A Full-Featured Customer Login Portal - Missing Steps?

I watched the How do I  video "Create a Full-Featured Customer Login Portal" several times, and have compared my code to the downloaded VB code.  I seem to be missing something.

I am trying to replicate what he does in the video, where he uses the login name to query another database and display the matching data.  In the video he starts by using a querystring (page.aspx?userID=name) before creating a login page..  My program works with this method.  However, later he creates the login page, and the system seems to automatically link the user database with the northwind database and give results without the querystring.  There is no indication of how this is done.  When I examined the downloaded code, he actually uses a session variable in the Page_Load event on the orders page.  There is no explanation of this either, just a quick "I'll paste this from the clipboard." 

I have compared my code line by line, and it matches exactly.  I can only guess that there is a missing step where a relationship is established between the ASPNETDB.mdf file and the northwind.mdf file.  Can anyone explain this to me?  Thank you.

My goal is to have a user log in, and the site automatically query the second database for that users statistics, and display them.