https://www.2checkout.com/documentation/notifications/order-created
It shows all the parameters that get passed so you can make a simple script to process it.
To enable 2CONotifications you need to do the following:
Login
Browse to the top right to an icon that looks like a "circle with horizontal lines inside" - Notifications.
Enter the appropriate URL for your IPN/Notification processing script (........
It was hard to find this as I find most online payment processors don't just put the basic information in plain view.
Remember to set your sid (your seller id). The below can easily be turned into a scripted PHP template to integrate into your own custom or existing payment solution.
http://help.2checkout.com/articles/How_to/How-to-Sell-Recurring-Products-with-2Checkout/........