Access to APIs and services on behalf of an organization requires System Administrator or Developer role.
Details on how to set up Developer role can be found here: https://helpx.adobe.com/enterprise/admin-guide.html/enterprise/using/manage-developers.ug.html
Users with those role can log into the Developer Console - https://console.adobe.io - and create integrations on behalf of the org.
Many APIs and services are only available with product license.
Access to the User Management API is only available to enterprise organizations
