Hi !
I went to canada last year for a student exchange, I was a little bit confused on how to get a visa, as you seem now. I suggest the best way to find out is to go dirctly on the Canada embassy website. I also discovered a student website which gives useful information about student visas, on which you coult take a look: http://beta.gullivearth.com/en/guide/administration_5/170/canada.
Good luck !
