Software to create a barcode is the last step in the process. You can easily create a barcode using a plethora of software tools but there’s no point in doing that if the barcode so created can’t be scanned by a supermarket checkout attendant. Therefore, the first step is to get a barcode from someone who propagates it to all supermarkets, so that it scans everywhere. That someone could be GS1, the only organization in the world that can give you an UPC barcode with your own Company ID :OR: a third party UPC reseller that will resell the barcode of a defunct product, so it will be on some other Company ID.