You can use AirPlay to watch movies playing on your device on your Apple TV. To Airplay a movie from your iPhone or iPad follow the steps:
1. Open the Cineplex Store app
2. Choose in your library the movie you would like to watch
3. Tap the play icon to play the movie
4. Tap the Airplay icon 
on the top right corner
3. Choose your Apple TV. If you don't see the Apple TV, ensure that your mobile device and the Apple TV are connected to the same Wi-Fi network.
To stop streaming, tap in the Cineplex Store app, then tap your iPhone or iPad from the list.