There are multiple options for restricting access to items that you place on Reserve
You can set a password for the course. Students will be required to enter this password when they try to add this course to their list of enrolled courses.
Additionally, you may enter ID numbers of the students in your course. If they are currently registered with Ares they will have access to this course. If they are not yet registered for the system, they will automatically be given access to this course when they do register.