1. Launch the App Store application on your device 
2. Click the Updates button in the top panel.
3. If a new update is available, it will appear in the list. Click Update next to the update description to download it.

If you can't update the game, please try these potential solutions. You can try them one by one - any of them might help:

1. Make sure you are not running out of free space on your hard drive.
2. Make sure your Internet connection is enabled and you have a stable signal.
3. Make sure the time on your device is set automatically.

• On your Mac, choose Apple menu > System Preferences, then click Date & Time.
  If the lock at the bottom left is locked , click it to unlock the preference pane.
• Click Date & Time, then select Set date and time automatically, then choose the network time server for your region.
• Click Time Zone, then select Set time zone automatically using current location.

4. Close the game and open it again.