You must register your device with a notification service, such as Apple Push Notification Service (APNS) for Apple devices, or Google Cloud Messaging (GCM) for Android devices.
In a production environment, when you register your application with the notification service provider, the device ID (iOS) or the registration ID (Android), is sent to the SAP Mobile Platform server. For iOS, the push certificate is stored there, and is used to authenticate push requests to the APNS server. When a push request is processed, that information is then used to target specific apps running on individual devices.