Configure Game Center
Enable an app version for Game Center
Once you’ve enabled Game Center in Xcode and configured your Game Center components, enable Game Center in your app version in App Store Connect before you submit the app for review.
From My Apps, select your app.
In the sidebar, click the app version you want to edit.
Select the Game Center checkbox.
You can now add leaderboards, leaderboard sets, achievements, and multiplayer compatibility to the app version.