I am assuming you have Terminal / Remote Desktop Services installed, and that your instructor has Admin permissions. (If not, give him permissions to the terminal services manager).
Open up Terminal Services Manager (Start, Admin Tools, Terminal Services, Terminal Services Manager), and then under the 'Users' tab, click on the user you want to see and then, on the right hand side, click 'Remote Control'. Just set your exit settings and you will be in.
As default, you do not have permission to remote control a session. To get control, go to Active Directory Users And Computers, and on the left hand side, click on your server. Then click the 'Users' folder. Right click the user you want to control, and click Properties. In the properties window, click on the 'Remote Control' tab and click 'Enable Remote Control'. It is recommended that If you do not want the user to know you are watching them, uncheck ' Require User's Permission'.
Let me know if you have any issues.