You may want to connect a Bluetooth® device to your Apple TV such as a game controller, headphones, a wireless keyboard, or another accessory.
Before you start, refer to the device’s instructions to set the device to discoverable.
To connect a game controller: Press and hold on Apple TV, go to Remotes and Devices > Bluetooth, then select the device in the Other Devices list.
See the Apple Support article Use your iPhone or iPad as a web camera with Apple TV