1. Click on "Orders" from the left menu of your Shopify Admin, then select the order number that you want to refund.
2. Click on "Refund Items" and set the quantity for the items to be refunded. If you're issuing a full refund, you need to ensure that both the upper and lower numbers match (number of items to be refunded/number of items purchased).
3. Click on the blue "Refund (amount)" button on the lower right to complete the refund.