From your teacher page click on "My Courses > View Course Catalog". From there, simply click the "Assign" button for whichever course you'd like students to be enrolled in. You can choose which section you would like to enroll in that course clicking on "Assign". You can then return to the course catalog or view the course.
It’s important to note that when you enroll students in an additional course, it will not be the main course for that section. The course will be added to "Assignments" from which you can edit, remove or unassign units from the previous course.
For more information on un-assigning and removing lessons visit: