On the Control Panel, expand the Users and Groups section and click Users.

Select Find Users to Enroll.

Type a username or click Browse to search for users. Only users that are not already enrolled in your course will be identified in a search for users.

Select a Role based on what the person is will be doing inside your course and leave Enrollment Availability set to yes so they can access your course.

Click Submit

This is not a permanent add. To get the user on your roster permanently contact Registrar.