To add users to the staff of a course, select the "Add new members" link from the upper left corner of the course management page (Courses management > Course Name > Add new members). The following window appears:
Type in the name of the user about to be enrolled and click on the "Search" link. The list of the names that match the search criteria will appear. If nothing is typed in, all the names of the users eligible as staff members will be listed.
Select the required members by checking the boxes next to their names and click on the "Add users to the staff" link at the bottom of the window.