Once he has a telegram account just go to https://LN.tips on his phone. It will open telegram and add the wallet. His lightning address by default is his telegram username@ln.tips and it also gives him an anonymous address if he wants to use that. You can also link the wallet to the Zeus or BlueWallet app to have a more familiar wallet app for sending and receiving. The tip bot dev is #[3]​ here on Nostr