how to pair an aluminum remote-?

For the old style Apple Remote (aluminum):

1. Unlinking any previous remote: press and hold the Menu and Left buttons for up to six seconds. On screen, look for broken link symbol above an icon of a remote.
2. Linking the (new) remote: press and hold the Menu and Right buttons for up to six seconds. On screen, look for a linked chain symbol above an icon of a remote.

If your Apple TV remote isn’t working - Apple Support - Wayback Machine (2nd half of the page)

• Point 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 Back button  and the Volume Up button  for 2 seconds.