Under the Settings, there is an option to match the Amazon Customers to the Intacct customers using some unique key. The integration will then automatically start mapping the customer using it.
In case the customer’s unique key from Amazon to Intacct does not fit, there is an option to create a New Customer under Order information page to Intacct through the integration.

But when this option to create new customers is disabled then, you’ll have a different option to manually map the customers between systems if the unique key is not getting matched or if you want to edit the mapping as per your requirements.