If you are using a DocuSign Sandbox environment for testing, this is how you can retrieve the DocuSignAccountID
.
Steps
Login to your DocuSign eSignature Sandbox environment.
Go to Settings > Apps and Keys.
Copy the value of the APO Account ID text field.
Apps and Keys page in DocuSign eSignature
Result
You have retrieved the DocuSignAccountID
of your DocuSign Sandbox environment.