You can find the affiliate in the Affiliates screen and click on API Details to view and copy this affiliate's info:
Once you click it you will see the details and have the option to "Copy & Close" at the top right
Username & Password - if you created their user you should have them, if they registered they should have it.
Api URL - Your Trackbox system URL
Ai - His Affiliate ID in 'Affiliates' screen
Ci -campaign ID, Recommend Ci=1
Gi - His Box ID in 'Boxes' screen
Our API documentation: Trackbox API