From the help document:
Labels with Barcodes
1 - You must have a label printer. A regular printer with Avery sheets will not work. It must be a label printer that prints one label at a time.
2 - Open the Products / Product Control window.
3 - The File menu is were the label options are located.
4 - Use the "Choose Product Label Printer" to select your label printer.
5 - You can design up to 3 label formats. Select one.
6 - Now you are in the Label Layout window where you can design your label.
7 - Put up to 8 fields on the label.
8 - For the Barcode field select UPC, Item# or whatever product field has your UPC's.
9 - Use the Font button to select your barcode font. The barcode font does not come with the POS. Usually a label printer will include some barcode fonts. If not, you can use the "Free 3 of 9" font available on the internet. You must also check the "Barcode Format" box. This tells the POS to add the start and stop characters to your barcode.
Tips:
Barcode fonts are printed in large sizes. Anything from 36 and bigger.
Set your label printer for maximum print quality.