The wrong Apple ID is auto populating when setting up my new Apple Watch. How do I change this Apple ID?

The person that you bought this watch from needs to follow all the steps in this link;

Remove the Activation Lock so that the buyer can use it.

If they can't or won't then get your money back or recycle the watch and put it down to a bad experience.

Did you purchase a used Apple Watch? If you did, it wasn't prepared correctly for a new user and ONLY the previous owner can remove the watch from their account. If you don't know them or can't reach them, you have purchased a useless watch, which you cannot use.

I got a new Apple Watch and when I get to the FaceTime setup it has an old invalid Apple ID on it. I’ve been to the Apple Store, had two. Hats and a phone consult. No one knows how to fix it. I’ll try this activation method next!

The same thing is happening to me. A brand new watch and it is using my deceased sons apple id. I have been trying to get past this since Christmas!