How do I pair Apple Watch 4 with AirPods

Read this....https://support.apple.com/en-us/HT207010

On the back of the case is a little button. Press it to put the AirPods into "Discovery" mode. The Apple Watch -> Settings -> Bluetooth display will see the AirPods.

Basically you can pair any Bluetooth headphones or speakers to the Apple Watch, by figuring out how to put the Bluetooth device into its "Discover" mode. I've paired Sony noise canceling headphones, a 15 year old Jabra headphones, and a 15 year or Insigna headphones to my Apple Watch. I had to do lots of googling for the 15 year old headphones. I still had the Sony instructions, and that button on the back of my AirPods made them the easiest to pair.