Here's how to use an Audioengine Bluetooth device to turn your 4th Generation Apple TV into a powerful home entertainment system:
First, make sure your Audioengine device is powered up and are ready to pair. Next, go into your Apple TV’s settings and choose Remotes and Devices. Then click on Bluetooth. Under Other Devices, you’ll see the Audioengine device (listed as Audioengine HD6, Audioengine B1, Audioengine B2, etc.). Click on that. Apple TV will pair with your speakers and will send the audio signal directly to the device.
A video link is here