To refund the entire order amount
Navigate to Orders > Search for order > click to open order detail > click 'Cancel' button from the top.
It will ask if you are sure, select yes. The order will show status is cancelled and you will see refund for total order on your Sales Report for today.
To create a partial refund, navigate to
Navigate to Orders > Search for Order > click to open order detail > click 'Edit' and edit the products or delivery charge on the order as needed. Scroll to the bottom of order to see the new order total to confirm it's what you expect, then click 'Save.'