How can I set up automatic payment

Here are the steps to setup Scheduled Payments,

Set up scheduled payments for Apple Card

1. Open the Wallet app on your iPhone and tap Apple Card.
2. Tap the more button , tap Scheduled Payments, then tap Continue.
3. Tap Pay My Bill to pay your previous monthly balance or tap Pay Different Amount to choose an amount. Then tap next:

• • If you chose Pay My Bill, select when you want your payment to be made, then tap Next.
  • If you chose Pay Different Amount, select your payment amount, when you want the payment to repeat, when you want the first payment to be made, then tap Next.

1. Confirm with Face ID, Touch ID, or passcode.
2. Tap Done.

If you want to change your scheduled payment, you need to first cancel your current scheduled payment. Just tap the more button , then tap your scheduled payment under Scheduled Payments. Tap Cancel Payments and tap Cancel Payments again to confirm your choice.

This support article also explains others methods to pay your monthly statement.

How to make Apple Card payments - Apple Support