to create your AWS Access Key and Secret Key.
That should be all that's necessary to connect NS FBA to MWS for handling Amazon Fulfillment requests.
Common things to confirm to make sure you can connect:
- You have active FBA service on your Amazon Seller account
- You have a Pro Amazon Seller account (and not an individual account)
- You created MWS credentials with the above link and specified "I want to access my own Amazon seller account with MWS." in the first step of the MWS registration