To customize the affiliate Sign up form with your own fields, follow the steps below:      

1. log in to the affiliate admin area and click "Set Up Software".

2.  Under “Set Up Software” and click on the link that says "Configure Sign Up Page".

3. Click on "Customize".

4. On this page, you can put a new logo or modify form accordingly.  

5. On this same page, you will see the second Option button beside Page Details which is  " Configure Form Fields" you can click on it and can modify or delete the existing fields or click the “Add New Field” button at the top to add a new field.