Using a couple of actions, you can add your own custom form fields to the Leaky Paywall registration form when a new subscriber signs up for a level. This code goes in the functions.php file of your theme or in a custom functionality plugin.
1. You must set up a page for registration and configure that page in the Leaky Paywall > Settings > General tab.
2. If using Paypal as your payment gateway, you must set the “Paypal Button Location” setting to use paypal on the registration form. This can be found under Leaky Paywall > Settings > Payments.