How to transfer money from my debit card to my Apple Card?
How to transfer Money from my ATM to my Apple Card?
iPhone 12, iOS 15
The Apple Card is a Mastercard credit card and you cannot transfer money from a debit card to it.
I suspect that you may mean Apple Cash rather than Apple Card. If so, see the following instructions to transfer money to Apple Cash from a debit card: Add money to Apple Cash - Apple Support