How to digitally download windows 7?

I have a 15 inch macbook pro, the base model, from last year, i got it in august. It runs lion. I want to play guild wars 2 and for that i need to download windows 7. I want to get the student price for it, but all i see are digital downloads and as far as i know, i need a physical copy to download it via bootcamp. I also dont know if i should get the 32 or 64 bit. Please help?