Yes, you do have the option to add and remove students manually if needed. Navigate to courses-->manage students and you will see the option to add student at the top.
If you would like to remove a student navigate to courses-->manage students where you can either manually locate the student or use the search students field to easily find the student. From there on the right-hand side you will have the option to delete the student if needed.
You can also delete a student under the show info tab.