How To Get Amazon Credentials
Amazon Seller Central
The store owner needs to get Seller ID, Access Key, Secret Key, and Marketplace ID from Amazon seller account. Please log in to Amazon Seller Central (for US) and Amazon EU Seller Central (for Europe) and go to Settings>User Permissions.
After arriving on User Permissions page, copy the Seller ID. Then, click View your credentials in Action Taken. A small pop-up window will appear.
Now, the admin can view Access Key and Secret Key as visible in the screenshot below.
Now, to get Amazon Marketplace ID, please visit this link and find Marketplace ID according to the region.