vi is super frustrating if you don't know your way around it. You get a sea of little tildes and you're supposed to know what to do? Eesh.
I recommend at least installing
gvim so you have a help menu, which you can use for reference. It isn't an IDE so you aren't cheating on your class. Do
apt-get install gvim -- when you can't remember how the heck you're supposed to open a dang file or save one, you can look at the menu. The keyboard shortcuts are listed on the menus. Just make sure that you actually type out the keyboard commands, even if you have to check a menu to remember them.
The really basic things that you need to know to avoid going insane:
- i puts you in edit mode so you can type
- esc takes you out of the edit mode
- :w saves your file
- :q quits the editor
- :q! quits an unsaved file
Other resources: this looks like a great getting started tutorial: http://www.openvim.com/tutorial.html as does the WikiBooks edition of Learning the vi editor