Easy peasy! At anytime you can assign an instructor - or multiple instructors to an existing student.
When logged in as a school, go to your prospect and student dashboard and click on student table.
Then click on the student. There you can see the student and their courses passed or in progress. You can also see their resume which indictates their experience entered into their logbook. You can also buy additional courses for this student.
Now click on associated Instructors. Select an instructor and click Add associated instructor. Not that if you are in the proess of adding instructors and they are not yet qualifed, you can still associate to a non qualified instructor for now. However the instructor will not be able to grade their practical skills untill the instructor is qualified.