Now it will be easier for Android users to watch Apple TV content on their TV with the addition of Google Cast support. However, even after this update, Google Cast is only an option on the Android version of Apple TV, not the iOS version. Likewise, the Android version still doesn’t support AirPlay.
If you’re not seeing an option to use Google Cast on your Android device, make sure you have the Apple TV app fully updated to version 2.2. You should see the cast button in the top right corner of your screen, next to the mute button on the “play” screen for shows and movies, and in the pause overlay on currently playing content.