There is currently no way to import service catalog information. However, users can create services and categories in multiple areas with the appropriate application permissions.
In the Admin application, a user can search/create services by locating Service Catalog > Services. The "New" button can be used to create a service, while clicking on an existing service will open up a page for editing. The Categories page directly above this displays a list of service catalog categories in their hierarchical structure, with the same actions available. A user with the Admin application can perform all of these actions.
In addition, these items can be created/edited from the Client Portal by clicking on the Services tab. The Categories link in the navigation bar displays a page that is similar to the one in Admin with similar creation/editing dialogs.
If a user has the Add Services permission, they can create new ones buy clicking on the "New Service" button. Similarly, if a user has the Modify Service Categories permission they are able to create new categories and edit existing ones.
Hopefully this helps to explain how service catalog content can be created, as well as some of the permissions around the service catalog that are enforced. Please let us know if there is anything else we can do for you.