On the Start New Game form, you may have noticed it says:
Leave blank to create an open challenge. Input a member name to challenge directly. Enter an email address if you want to challenge someone who is not yet a Chess.com member!
If you have Gary Kasparov's email address, you can send him a challenge. If he follows the link, signs up to chess.com, you will have made a successful referral.
What are you waiting for?
Information request- In Profiles , what are referrals please?