iOS prompts for permission when your app calls application:registerForRemoteNotificationTypes:
generally called in your Application's application:didFinishLaunchingWithOptions
method.
Don't forget to send the device token to your APNs server in the application:didRegisterForRemoteNotificationsWithDeviceToken:
delegate method.
You will most likely need to update your app to add such functionality, and update the App ID and provisioning profile to allow APNs.