You need Amazon Affiliate ID to track and get sales commission from Amazon. To get Amazon Affiliate ID you need to join Amazon Affiliate Program - its free.
Here is the link to getting started - https://affiliate-program.amazon.com
Select your country specific Amazon Affiliate Program and signup. Once inside the dashboard you will get your Affiliate ID.
Lastly, save the Affiliate ID in the settings section of Spreadr dashboard.
Thereafter, all the sales generated will be credited to you.