If you did not see the Enter Credit Card Details button directly below the Payment Method drop-down when creating a Sales Receipt or Receive Payment, you need to setup your credit card payment methods to use merchant services. If the Process Credit Card check box is greyed out, make sure the credit cards you accept are active on your Payment Methods List. Here's how: 

  1. Go to the Gear Icon > Lists.
  2. Click the link for Payment Method List.
  3. In the Action column for the Visa or MasterCard options, select Edit.  
  4. Check the box This is a credit card option to select, and then click Save.
You can also add a new payment method option and then make sure that you mark the Credit Card option.

The Enter Credit Card Details button should now be available so that you can edit your credit card information.

You will also need to select the option Process Credit Card under the Payment Method drop-down on the sales form. When you save the transaction you will see a pop up letting you know if the transaction is approved or denied.