Amazon MWS Auth Token

I’m attempting to use the Amazon integration as outlined here: https://erpnext.org/docs/user/manual/en/erpnext_integration/amazon_integration

Where can I find my MWS auth token and Domain? Do I need to register as a developer on Amazon for this?

Thanks for any help with this!

https://docs.developer.amazonservices.com/en_ES/dev_guide/DG_Registering.html