Apple watch

Is it your Apple ID?

• Yes. If you forgot your Apple ID email address or phone number - Apple Support
• No. The Apple Watch is Activation Locked. The original owner must assist you or the watch will remain useless forever.

You can ask apple to remove the activation lock online on this page;

Online Activation Lock Removal Tool.

Or this;

If you can't remember/gain access to the apple id that paired the watch to the phone.Take the watch and it's receipt with the serial number along with some photo id and any other proof of ownership to an Apple Store and request that they remove the Activation Lock for you.