Step 1: Go to your control panel (admin.epc)
Step 2: Click the Invoice Report link in the sales section
Step 3 : Select a range of invoices to locate the invoice in question, or click the 'find invoice' link in the sales section and enter the order number directly.
Step 4: Once you see the invoice summary, click the invoice number link to display the order
Step 5: If you want to change the ship to address, add a discount, change shipping method or something relating to the invoice header (not part numbers), you click 'edit invoice header', if you want to edit the qty on a part, or change a price, click the link called 'edit detail'.
Step 6: The edit screens in the invoice section work the same as part numbers, pricing, and other maintenance screens. You are shown the fields in the file, with the ability to edit each field and then click save.