Well, it's like magic. Check it out. When someone registers they will see this question, 'If someone invited you to register, tell us who so we can give them credit.'. They will type in your name and then select it from the results.
Remember, your name will be as it appears at the top of your P2P page.
Even better, provide them with your challenger URL, like this:
https://p2p.onecause.com/kidsmuddymadness/accept?challenger=octavia-harston