To add many students at one time, click Add multiple students.
This gives you the option to bulk import a list of students. Add a list of students and admins emails to a list by entering full name, email.
This can also be done by copying a CSV file with the same name and email format.
This option can also be used to add students from a previous course, by simple copying (ctrl+c) them from the participant-list of the old course.