As per blow from Apple. Do not use the Watch so guessing similar would need to be done for computer
Unpair your Apple Watch
When you unpair, your iPhone will try to create a backup of your Apple Watch. When your device returns from service, you can use the backup to restore your Apple Watch.
Follow these steps to unpair your devices:
- Keep your Apple Watch and iPhone close together.
- Open the Watch app on your iPhone and tap the My Watch tab.
- Tap All Watches at the top of the screen.
- Tap the Info button
next to the watch that you want to unpair. - Tap Unpair Apple Watch. For cellular models, tap Remove [Carrier] Plan.
- Enter your Apple ID password. If you forgot your Apple ID password, you can reset it.
- Tap again to confirm.