1. Create a Credit Note about the returning goods. If you are doing this for your supplier, create Supplier Credit Note instead.
2. under Reason on the right, choose Goods return. 
3. Once done, click Save.
4. go to the invoice that you wish to apply the return goods and click Edit
5. under payment tab, click Use a Credit Note. (to learn more about how to apply CN, click here)
6. choose the CN that you wish to apply. Once selected the CN, tick the checkbox for "Return the goods into inventory".
7. click Use.
8. You should see the goods is returned when you view your product's Inventory Log.