In order for it to work, you custom mobile app needs an App Id, which is a string that is set during development.
You will need to setup your iOS Bundle ID and the push settings for iOS.
Custom iOS mobile apps require an Apple Push Notification Authentication Key for push notifications to work. You can create one at developer.apple.com from your Apple developer account.
Insert the Apple Team ID, Authentication key ID an Authentication key data. Once you filled all this in, just select the Authentication key file and click save.