There'll be a designated Standard Chartered Branch in Karachi, Usually it's the main branch in the city. Go there, there'll be Canadian Embassy Payment Slip, Each slip will have 4 leaflets, take them, fill them with info, Your name, DOB, passport number.
Tick Study Permit, than write 1 and 8700 in front of fields
Than, write Processing Charges, I think, 494
Add Total Amount and write it, sign it, Select Cash if you are paying cash, Tick account if using SCB account to transfer money.. get a token, pay the fee and you r done!!
You'll get two slips back, send green one to embassy, Yellow will remain with youy