2Checkout Problems

I am trying to activate Marketpress to work with my 2Checkout account. Your instructions are very unclear though. You ask for a "Seller ID" and say I have to go to a dashboard, there is no such dashboard in 2CO there is only "Site Management" which contains the secret word but no "Seller ID". I assumed the "Seller ID" was my 2CO username and used that.

On the setup page you say the following: "Resell your inventory via 2Checkout.com." What the hell does that mean? Will it work as a shopping cart or not? Or is there something else here I am missing?

Also please help me understand if I should create a product in my 2CO account that match the products I create in Marketpress? How does that work?

I have setup the account as best I could. When I run a test in demo mode, I get a "Cart Empty" message on 2CO. Please test here: http://www.careerdevelopmentplan.net/shop Why is this happening?