What if you don’t know the Apple ID and password

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

Remove the Activation Lock Here.

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.

Are you the original owner of the Watch, or did you purchase this from an individual? If you are the original owner, you will need to recover your Apple ID and password. It should be the same one as your iPhone. If this is a second hand devices that you purchased from someone and it still has their Apple ID on it, you have encountered Activation Lock. You will need to contact them to remove the Activation Lock or the device is useless to you and you will not be able to remove the Activation Lock.