If you are already in Canada when the new visa requirement came into effect, you can remain in Canada, subject to the terms of your visitor record, work permit or study permit.
If an extension is required, you are required to make an application to CIC’s processing centre in Vegreville, Alberta, before the expiry date on the document.
If, during your stay in Canada, you choose to travel anywhere outside of the United States or Saint-Pierre and Miquelon, while your work permit, study permit or visitor record is still valid, you will need to apply for a Temporary Resident Visa to re-enter Canada