Some costs are easire to account for manually. To change the Cost of any part of your order you have to go to the Orderlist. Link
On smaller screens you might have to scroll to the right to see a little pen icon. By clicking on the pen icon a window will that shows you all the costs attached to the selected order.
Once you have made the appriopiate changes click on Save. The changes have now been saved. The Cost Source will change to 'Manual'