• You should be able to update the game from App Store by searching for Royal Kingdom.
• After opening the page of Royal Kingdom, you can see the "Update" button on the page.
• You can update the app by tapping on the "Update" button. 

Note: If you cannot see an "Update" button on the page;

• Open the App Store,
• Tap on your profile photo at the top right side of the screen,
• Swipe down the screen,
• Tap on the "Update" button next to Royal Kingdom,
• After tapping the button, you will be able to update the game.