The Siri Remote comes automatically paired with your Apple TV. If it disconnects or you get a replacement remote, you’ll need to manually pair it to Apple TV.
You can pair the Siri Remote with only one Apple TV at a time. When you pair a remote, any other paired remote is automatically unpaired.
Turn on Apple TV and position the Siri Remote so it’s within 8 to 10 cm (3 to 4 inches) and pointing at the front of Apple TV.
Do one of the following:
Siri Remote (2nd generation): Press and hold the Back button for 2 seconds.
When the Siri Remote is successfully paired, an onscreen message appears.