Yes, you enroll for the Costco promo code at www.Costco.com. Then you would sign-up for a new account at www.moviepass.com/costco using the promo code. You must use a different email address from the address used for your monthly MoviePass subscription. After you are successfully enrolled in the program, you can cancel your old monthly subscription in the MoviePass App by following these cancellation instructions.
Keep in mind that MoviePass cards are expected to be fulfilled 2 weeks after registration.