You can refund non-disputed payments directly from the Dashboard.
To refund a payment:
Go to the Payments overview page and find the charge to be refunded.
Click the three dots icon next to the charge and select "Refund charge".
Enter the amount to be refunded. The default is a full refund. If you want to issue a partial refund, enter the specific amount.
Choose a reason for the refund. If you select "Other", you will need to provide an explanatory note, which will be attached to the refund.
Click "Refund" to process the refund.
For more information, you can read here: How to Refund a Customer