This is "Confirmation to Work Off-Campus" Letter. You need to get it from CIC. You can apply for it online from here: https://dmp-portal.cic.gc.ca/enquiries-renseignements/canada-case-cas-eng.aspx?_ga=1.170578208.1079316027.1379171408
Yet you are not authorize to work as you are not enrolled as full-time student. You will need "Letter of Registration" or "Letter of Enrollment" from your school stating that you are Full-Time registered student and with that letter you are all set to apply for "Confirmation to Work Off-Campus" letter from CIC. The timeline written on CIC website is 30 working days but normally you will get it within 10 working days.
and Welcome to Canada