URGENT Help Needed with GitHub Plugin

I'm using PaidMembershipsPro. I need to add two required fields to the signup/checkout. The only way I have found to do this is with the plugin extension Register Helper on GitHub (can't post the link) I've uploaded the master folder from that and activated the plugin. But I can't figure out what code to put where on the plugin php file and/or checkout page! Please, please - tell me if you can definitely help me get this to work (I will need to do this for client on several sites) and how much you'll charge me so I understand what I have to do to get this to to work. Thank you. Skype is a big plus!