Step 1 of 9: Getting started: Create a Game Centre Account

If you don't already have a Game Center account, you'll need to make one. Game Center gives you a 'nickname' by which is what you're known on the platform – it connects to your Apple ID, but unlike your Apple ID, can be changed at any time (we’ll cover this later)
One you open Game Center, a dialogue box should open, asking you to connect your Apple ID with your Game Center account. If you don’t have an existing account, you’ll be prompted to create one. Read about iOS Game Center.
Note: If at any point ‘Account’ says ‘(null)’, it means your Apple ID is not connected to your Game Center account. You’ll need to sign in again – click it and a screen like below appears.