How to sign up and keep track of affiliates.

I have an ecommerce website powered by Zen Cart. A webmaster arranged for my site to allow and keep track of sales that are directed to my site by affiliate sites. I have forgotten how to get to that area on the backend of my site. I wish to sign up some affiliates but I'm not sure how to do it. I need to find someone who can teach me how to sign up the affiliates and how to keep track of what I will need to pay the affiliates. I would also like to add text to my site which would let others know that they have the opportunity to be paid for directing people to my site.