1) When you're taking an in-person order and 1) have all the products in the cart and 2) the customer selected, click checkout at the bottom of the screen.
2) You'll then be directed to the Select payment type screen where you'll select "Credit card (manual entry)".
3) Enter the credit card information in the next screen and once you've filled out all the fields, click the "Charge" button at the top right of the screen.
4) The transaction will be processed and you'll then be directed to the Payment Successful screen reflecting that the order has been paid.