Amazon Marketplace Web Service (Amazon MWS) is a secure environment that uses signatures for authentication and lets sellers delegate calling rights to developers by using the Amazon MWS authorization service. Before you can develop Amazon MWS applications for yourself or others you must register as a developer on the User Permissions page in Seller Central. See Registering as a developer. To be eligible to register for Amazon MWS, you must have a Professional selling plan. For more information, see Selling plans in the Seller Central Help.

Registering as a developer

Before you can develop Amazon MWS applications for yourself or others you must register as a developer.

To register as a developer

1. Go to the User Permissions page in Seller Central and log into your Amazon seller account as the primary user.
2. In the Amazon MWS Developer Permissions section, click the Register as a developer button.
3. Fill out the Register as a developer form.

Be sure to click the Verify button to verify email addresses that you enter.

4. Click the Sign up button.

Your Developer ID appears.
5. Click Your developer credentials - Do no share these.

Your AWS Access Key ID and Secret Key appear.

You can access your Developer ID and developer credentials at any time on the User Permissions page in Seller Central.

For more information on how to use the Developer ID and developer credentials. Please visit the below link.
https://docs.developer.amazonservices.com/en_IT/dev_guide/DG_Registering.html