In order to connect your GoDataFeed store to your Amazon account, you’ll need to authorize GoDataFeed's app. 

Authorizing an app requires the Amazon Seller Central account owner

Use the following instructions to authorize GoDataFeed to access your Amazon account using Amazon MWS. This will allow you to use these GoDataFeed solutions:

• Import products from your Amazon inventory into GoDataFeed
• Submit product feeds to Amazon to create, update and remove listings and inventory
• Sync orders from Amazon with your store 

At the end of these steps, you will be provided with your Amazon Seller ID and MWS Authorization Token which will be used to submit your feeds, sync orders, or import products. 

Step 1 Launch the authorization process and confirm the Developer Name and Developer ID , click Next

Select which region you are using. Repeat this process for each region you require. 

Connect Amazon North America

Connect Amazon Europe

Developer's Name: GoDataFeed

Amazon US Developer ID: 379788198321

OR

Amazon UK / EU Developer ID: 094479053376

Step 2  Accept the terms and click Next

Step 3  Your Seller ID, Marketplace IDs, and MWS Auth Token will appear

Step 4  You can now navigate to Feeds > Select the feed > Settings> Scroll down on the right and you can copy and paste these into GoDataFeed - you're all done!

Amazon MWS endpoints and MarketplaceId values

 The following is from Amazon Marketplace Web Service (Amazon MWS) Documentation