If you'd like to share individual course codes that would make it so that only one course is on the student's dashboard, you can do so by following these instructions:
1) Once you create a class with multiple courses for the first time, after clicking Share Registration Code, you then will select Show Registration Code for Individual Courses.
2) You can then copy the code for the individual courses and provide the code to your students so they can register for just that course.
If you'd like to share an individual course code after creating a class for the first time, please follow these instructions:
1) Go to My Classes up in the top navigation bar
2) Click on Registration Code for the class you would like to get individual registration codes for.
3) Click Show Registration Code for Individual Courses
4) You can then copy the code for the individual courses and provide the code to your students so they can register for just that course.