Affiliate + Cart Integration

I have Cart and Affiliate installed and working perfectly on my domain, but integrating Affiliate with Cart is not working.  Specifically, I am trying to send commissions to Affiliate from Cart when a sale happens.

There are a few confusing pieces in the docs.  In Cart: Store CP/ Settings/Settings Menu/Maian Affiliate Integration/Affiliate Product ID.  What is the Affiliate Product ID?  Is this some kind of KEY?

Also, the information on this How-To:  It says you have to add this code into some file to make it work.  It doesn't say which file, or where.

I am going to buy the commercial for both Cart and Affiliate as a start, but I need to make sure it works as needed, before that happens.


P.S.  Your product so far is wonderful!  Very clean, and easy to use so far.  Great work!