Create php script for affiliates for my site

I have this site: [login to view URL] At the bottom of the site I have "Affiliates" button. When you click on it, it appears a text and then "under construction". When someone wants to register for my affiliate program, in order to earn 75% for every e-book sold, he needs to have a form to complete, or to register. I don't know how to do this, that's why I want an expert in coding. My gateway payment is via paypal. I attached the "php" script in notepad for you to see if you can add more scripts to it for doing this job properly.