Amazon MWS Setup Instructions
 ​The Amazon Marketplace Web Services (MWS) keys are required in order to pull your product listing information from Amazon and also to integrate FBA inventory levels and order fulfillment. To set up the integration with Amazon MWS, follow these steps:
  1. Go to ​​​​ .
  2. Click the Sign up or Manage MWS link.
  3. Log into your Amazon seller account.
  4. Scroll down to Amazon MWS Developer Permissions, click the yellow button for Authorize a Developer.
  5. In the Application Name text box, type CoMerchant.
  6. In the Application's Developer Account Number text box, enter 5487-5604-2612.
  7. Click the Next button.

Accept the Amazon MWS License Agreement and ​click the Next button.
Copy & paste your Seller ID and MWS Auth Token into the appropriate fields on the signup form.