Check whether the caller is authorized to make the call
Process the incoming XML message using a Mendix mapping file
In case a recipient of the envelope completed the signing process, get the documents with a REST call to the DocuSign API. You can also choose to get the DocumentPDFs in the incoming XML message but those calls are getting really big then.
See the documentation:
Feature: Save signed documents in your Mendix app (when using embedded signing).
Limitation: Saving documents that are signed through remote signing is not yet possible.