If you are using iOS 13 on your Apple device and you are over the age of 13, you will be able to connect your current account to Apple Sign-In.
In order to do so, you will need to open your in-game Settings Menu by tapping on the gear icon on the top left side of your in-game screen.
Once you open up the Settings Menu, you can find the ''Sign in with Apple'' option. Simply tap on it and your account should then link to Apple Sign-In.