Open iOS Developer Portal in your browser.
Navigate to the Identifiers tab.
Select App ID's section and click on your App Id linked to your project.
Click on Edit/Configure button (In-case if you see this disabled, you may not have required access).
Enable iCloud service and Save.
A note on Entitlements if required. !!!!
For more information, please refer iCloud Setup Guide.
Cloud Services on Android rely on Saved Games feature of Game Play Services. To enable it make sure you enable Game Play Services first. You can see this setup in Game Services Feature.
In Google Play Developer Console, enable your game for Game Play Services.
Once after setting up Google Play Services, go to your Game Services tab.
Click on the app you want to enable Cloud Services.
Select Game Details tab.
Enable Saved Games toggle if its not enabled.
Click on Save at top left.
For more information, please refer Enable Saved Games.