How do I add my bank account to Apple Pay- Card

Are you want to transfer funds to you Apple Cash virtual card in your Wallet app? If you add a debit card to you Wallet app it can be used to make instant transfers (there may be a small fee). You can also transfer directly to your checking or savings account. These are usually not instant and a fee may apply. Please review the support article linked below.

Transfer money in Apple Cash to your bank account or debit card - Apple Support