How does Apply Pay connect with bank account ?

ayumi34 wrote:

So, should I set up interfacing with my credit card?

All you need to do is add the card to your Wallet. When you make a purchase using Apple Pay by double tapping the side button, it will automatically bring up the Default Card that is set at Settings > Wallet & Apple Pay > Default Card. If you want to use a different card then the Default Card, you can select it first in the Wallet app, then hold it up to retail terminal that accepts Apple Pay and it will use that card instead.

More information about using Apple Pay after your card is set up is available here:

Use Apple Pay for contactless payments on iPhone - Apple Support

What cards do you have in the Wallet app?

Set up Apple Pay - Apple Support

Apple Pay is built into iOS, but needs a payment method that you provide to make the transaction.