Any barcode value in GroovePacker can be printed as a scanable barcode right from the product page. Open the product page by clicking the product name in the products list.
If there are multiple barcodes saved for the product the first in the list will be printed. To print another barcode simply drag and drop it so it appears first. The first barcode is considered your "primary" barcode which is the one displayed in other areas of the app.
If you do not see a tab open with the barcode after clicking the icon please check your browser URL bar. If there is a "blocked popup" icon you may need to click it to enable pop ups for your GroovePacker domain.