How do I remove the "Enter Passcode" from my Apple watch?

You would enter the passcode. Watch requires a passcode.

If you do not know the password, reset the Watch passcode.

If this is a Watch you have purchased used and have not already been successfully using this Watch prior to this passcode prompt, and have now encountered Activation Lock, then you will want to discuss the transfer of ownership with the seller. If the seller of this used Watch is no longer available, no transfer of ownership is available and Apple won't reset the Watch absent convincing proof of ownership. If the Watch is locked by Activation Lock, then the Watch will not be useful to you.