It's run through ShareASale [1]. They take care of tracking sales, cutting checks, sending 1099s at the end of the year, and all the other boring parts of running an affiliate program. As for getting affiliates interested, there's a link to the program in the footer of the site and a link within the app for existing customers. When I come across a site that seems like it'd be a good fit for some kind of partnership, I just send a brief e-mail and see if there's any interest.
1: https://www.shareasale.com