To connect your seller central market place to seller chain follow these steps.
1. Navigate to the top right corner of your Seller Chain page, where your marketplace name is displayed. Click on 'Manage Marketplaces,' and it will direct you to the required page.
2. Once on that page, locate and press on "API Disconnected." Following that, press "Connect Account.
After pressing "Connect Account," it will take you directly to Amazon. There, you'll need to agree to some terms and save those settings.
Once all that is done, your account will be set up. It will take some time for the listings to get in, So If you want to create a shipment right away, you can use the 'upload file' option.