How my Apple Card can work on Apple Watch

For information on paying with Apple Watch, see the following from: Make purchases using Apple Pay - Apple Support

Pay with your Apple Watch

1. Double-click the side button.
2. Your default card opens automatically. Scroll down to choose another card.
3. Hold the display of your Apple Watch near the contactless reader until you feel a gentle tap and hear a beep.

Also see the "How to add a debit or credit card to your Apple Watch" section of Set up Apple Pay - Apple Support

Open the Watch App on your iPhone. Tap My Watch (lower left corner). Tap Wallet & Apple Pay. Choose your Apple Card and make sure View in Wallet is on.