Before applying for a study permit you need to make sure you meet the entry requirements for all people entering Canada. You may need a Temporary Resident Visa (TRV) to enter Canada, even if you have a study permit.
The Canadian educational institution where you intend to study must formally accept you as a student before you can apply for a study permit. Once accepted you must complete the following forms:
1) IMM 1294 - Application for a Study Permit
http://www.cic.gc.ca/english/applications/student.html
Applications should be sent to the Canadian High Commission, Embassy or Consulate which covers the region you are applying from.