There are two types of barcode that can be added to your integrated labels - a single "template" barcode that can be added to your design, and product barcodes that can be included in your products table.
The template barcode can be freely added anywhere on your integrated label design. Simply, drag the Barcode element onto the page and resize to fit as needed.
From under Advanced Settings, you can select whether the barcode is generated from the Order ID or Shipment ID and in what format the barcode is generated, e.g. CODE-128 or EAN-13.
Product barcodes can be generated and included in the products table, just ensure that the Barcode column is selected under the Product Table Fields menu.
The barcode is can be generated from the product SKU, Name or Barcode value field (if populated). You can select which by selecting Advanced Options in the bottom left of the page.
You can read more about how Shiptheory receives and updates your product data, here.
If you have any questions, just get in contact with our support team who will be happy to help.