How To Combine Orders
If a customer purchases multiple items you may wish to combine them into a single order. To do so, put a check in the box to the left of each order that should be combined, then click the Perform on Selected button, and select Combine.
This will add the products to a single order, and combine the shipping costs. You may need to then edit the order to apply any combined shipping discounts manually, and the order may only show a partial payment. Once the order has been edited to show the revised shipping and it matches the amount paid, the order will show as Paid-In-Full.