Hope this helps. I'm not an expert, a retailer as well using QR codes. So, I created a sku number when created the item. copied it. then in my printing program that creates labels, there is an option to add a QR code on the label, I paste the sku number I created on the items in that box to create the QR for that item.
When you check out in square, hit the search box, scan the QR code you crated on label, and your item should pull right up.
This is how I do it as I use the free version right now getting started. Good Luck
