Summary: 

To edit existing product codes in Unleashed one at a time.

Steps:

• Click Inventory on the side-bar menu
• Click Products 
• Click Change Codes
• Click on the Single tab 
• Type in existing product code in *Product field
• Type in new product code in *New Product Code 
• Click Save

Additional Information:

There is an option to update them by batch. 

Instructions can be found under the Batch tab, or click here.