Affiliates and Directory Plugin integration

Hi I just installed the affiliate plugin onto my site. I would like to use it with the directory plugin. Our listings are behind a paywall via paypal. We want to get some help from affiliate members to help sell listings. I installed the plugin and integrated it into directory but I am uncertain how it works. Do I need to send out a separate email to my community. How/where do people sign up to be affiliates exactly? Membership is free and people signup via gravity forms.