Missing Authentication Token for createRestrictedDataToken operation

Executing the POST method of the createRestrictedDataToken operation of the Tokens API. I always get the same response: "message": "Access to requested resource is denied.", "code": "MissingAuthenticationToken".

I'm not sending any authentication token information in my POST call because there are no instructions telling how, when or where to do that. What am I missing?

Or, am I asking for access to the wrong path/data elements? I have set up my user and added roles within IAM management. Is that where the autehntication comes from?