Extending your stay in Canada requires a completed Application to Change Conditions or Extend Your Stay in Canada. This application is available from Citizenship and Immigration Canada (CIC). You should apply for this renewal at least 30 days before your study permit expires.
If you apply for a renewal and your permit expires before you receive an answer, you can continue to study in Canada until you receive a decision.
You cannot extend your study permit beyond the expiry date of your passport.