Obtain proof that you've enrolled and been accepted to an Italian university, along with a schedule of when your classes begin and end. This should be either with the official seal of the university or a signed and notarized copy from the school.
Ask your health insurance company if your insurance will cover you if you're in Italy. When you know it will cover you, get proof of your health insurance
Gather your recent bank statements and/or proof of income. You must prove that you have the financial means to support yourself while you're studying in Italy.
Take your information to your local Italian consulate, and you will be told if you have everything you need.
Fill out your application with the Italian consulate and you should receive your visa.
Check in with the local police when you arrive in Italy to register your arrival with your student visa. This will make Italy your legal residence for one year.