I bought this watch on line and don’t have the Apple I D ..what can I do ?

there is not much you can do

activation lock is not a thing on the watch it's a theft protection on apples servers

it needs to be removed

About Activation Lock on your

Apple Watch - Apple Support

if you don't know your appleID password If you have

forgotten your Apple ID

password – Apple Support (UK)

then you will need the assistance of apple Activation Lock - Support

(apple.com)

and or

 Apple Support

And or

 Contact - Official Apple Support

and or

Genius Bar Reservation and Apple

Support Options - Apple

Rudegar is correct on all points.

I'd like to add:

1. Contact the seller to see if they can help you. If it was their watch, they can remove it from their list of devices using Find My.
2. If it wasn't their watch (i.e. they found it), then there isn't anything that they can do to help you. Ask them for your money back.

What to do before you sell, give away, or trade in your Apple Watch, or buy one from someone else - Apple Support