How do I unlock the activation lock

Here are two ways to unpair your watch if you no longer have the paired iPhone:

• See the 'How to erase your Apple Watch if you don't have your iPhone' section of:

Unpair and erase your Apple Watch - Apple Support

• With a web browser, go to: https://www.iCloud.com and sign in with your Apple ID. Open Find My iPhone and select All Devices (at the top). Then click your Apple Watch, select 'Erase Apple Watch', and select Next until the device is erased. Finally click "X" next to remove your Apple Watch.

This support article has information about Activation Lock on your Apple Watch and how to turn it off as part of preparing a Watch for service or a new owner. --> About Activation Lock on your Apple Watch - Apple Support