Click on the Profile Icon and navigate to Financial > Payments
Select the payment you want to refund.
Once on the payment profile, click the Refund button.
Select the appropriate options on the refund screen.
When finished, select the Process Refund button at the bottom of the screen. The refund is dropped into a disbursement group and needs to be placed in a disbursement batch and paid. These are separate processes that will be discussed elsewhere.