Apple's return policy for an Apple Watch that has been purchased directly from Apple can vary by country.
In the US, for example, Apple's policy allows for returns within 14 calendar days of receiving the Apple Watch:
If you need help, then contact Apple:
(Note that you are not talking to Apple here - this is a user-based technical support community).
Other retailers' return policies may vary. If you bought your Apple Watch elsewhere than from Apple, check with the retailer to establish any available return options.