Connect the Siri Remote to Apple TV
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.
Pair the Siri Remote with Apple TV
Turn on Apple TV and position the Siri Remote so it’s within 3 to 4 inches (8 to 10 cm) and pointing at the front of Apple TV.
Press and hold the
button and the Volume Up button 
for 2 seconds.When the Siri Remote is successfully paired, an onscreen message appears.