Registering a seller account Is pretty easy. You'll need specific things depending on your country, etc.. Here's what I got from a quick Google search. You can use your Ssn as EIN and then change it later or you can register for an EIN for free in a few minutes. Outside of that depends on the country
Steps to Register:
Navigate to Amazon Seller Central: Go to sellercentral.amazon.com and click "Register now".
Create an Account: Follow the prompts to create a new seller account.
Online Interview: As an international seller, you'll participate in an online interview to determine your tax obligations (W-8BEN for non-US taxpayers or W-9 for US taxpayers).
Account Setup: Once approved, you'll set up your Seller Central account and begin listing products.