U need to have an "Offer Letter" before you apply for "Study Permit".
Step 1: Apply to any college of your Choice.
Step 2: Wait for approval and an Official "Offer/Acceptance Letter" from the College.
Step 3: Apply at your nearest CHC (Canadian High Commission) for a Study Permit.
For more information, go to
cic.gc.ca/english/study/index.asp