Your master catalog is the universal inventory where all the products that you're selling on different sales channels are stored. On the other hand your channel catalog only lists those products that you are selling on a particular  channel.

You can link your sales channel catalog to your master catalog in two ways;

1. Products tab

  •  Go to Products--> Channel in the Shiprocket panel
  • You will find the unmapped products that are not yet added to the master catalog under the tab Unmapped.
  • Click on the Map button under the Actions section on this page.

2. Orders tab

  • Go to the Orders tab in the left panel
  • Click on the Unprocessable tab from the top level tabs. Here you will find a list of orders that couldn't be processed because of either being out of stock or not mapped to the master catalog. The status section on the page helps in differentiating between the two and shows a Map button against the products that are not yet added in your master catalog. 
  • Click on the Map button against a product to add it to your master catalog.