To add money to your Cash App card at an ATM, you'll need to first deposit cash into a bank account linked to your Cash App. Afterward, open the Cash App, navigate to the "My Cash" tab, and select "Add Cash." Enter the amount you wish to transfer from your bank account to your Cash App card, and confirm the transaction. Currently, Cash App doesn't support direct ATM deposits, so using a linked bank account is necessary. Ensure your Cash App card has sufficient funds before making any purchases or withdrawals.