Before using these options you must open an account with the vendor and install their app on the iPad.
Tap the Credit Card Processor selector
Choose the credit card processor.
To process a credit card with the selected credit card processor:
Go to Sales
Create or open the invoice
Change the Payment Method to Credit Card
Enter the Payment Amount and tap Accept Payment
You will be given the choice of processing the payment with the selected credit card processor or just enter the payment manually.