Related information
In order to configure and enable push notifications for iOS apps, you need to first generate and obtain the following:
Note: An Apple Push Notification service (APNS) Certificate is required when using push notifications to propagate data between the server and an iOS mobile device. Information on generating an APNS Certificate is available in the iOS Developer Library.
The single private key and a single APNS certificate must be saved in a P12 file so that it can be uploaded and saved in a certificate set for the iOS custom app you are creating - see Configuring push notifications on iOS.