Final answer:
End users access the service catalogue in the Service Portal either by 'Under Request Something' or via the 'Service Catalog link', depending on the portal configuration.
Step-by-step explanation:
When end users are utilizing the Service Portal, they typically access the service catalogue by selecting either Under Request Something or Through the Service Catalog link. The options available depend on how the Service Portal has been configured by the organization. There isn't typically a separate Service Catalog App within the portal, and services are not accessed via Tickets. End users browse the service catalog to request new services or report issues, and the catalog can include items such as hardware, software, and support services.