How to setups Apple Watch using activation lock

Take it back to the seller and get them to do all the things in this support article, or ask for a refund. --> Before you buy, sell, give away, or trade in - Apple Support

This support article has information about Activation Lock on your Apple Watch and how to turn it off. --> About Activation Lock on your Apple Watch - Apple Support

Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Do this online at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not state what currently constitutes proof. Prior to this new online service Apple typically required the original receipt issued by an Apple Authorized dealer and documented provenance (so typically it would be the original owner who does this, or a descendant with legal proof of ownership). Apple recommends you keep your receipt after you buy an Apple device. --> Keep your receipt after you buy an Apple device - Apple Support

iF your Apple Watch is activation locked either enter the correct information of the Apple ID tied to the watch, and if you don't have access to that information, and you're the original owner and can provide valid proof of purchase information,  you can start an Activation Lock support request.