Follow the steps laid out in this Apple doc.

Troubleshooting:

If you encounter the following error: Command CompileAssetCatalog failed with a nonzero exit code, then ensure you have created a new App Icon asset for your new platform.

Create App Icon as needed

iPhone Settings

If adding iPhone support, ensure that you add the UILaunchScreen to the Info.plist as seen below.

INFOPLIST_KEY_UILaunchScreen_Generation = YES;