Download the JackPad app separately to use your iPhone or iPad as a controller. For single-player games, you can play on your Apple TV and use your device as the controller, without the JackPad app. Two ways to play:
1) On your TV – connect your iPhone or iPad to your Apple TV via Airplay. Then use your iPhones or iPads as controllers.
2) On your iPad or iPhone – use your device as the screen that everyone watches, while using (different) iPhones or iPads as controllers.