You should apply for a study permit before coming to Canada. Make sure you have a letter of acceptance from a designated learning institution in Canada before you apply.
You should apply online for a study permit, whether you’re outside of Canada or already in Canada. If you can’t apply online because of a disability or because there’s a  problem with the online application, you can apply on paper.
If you’re currently a visitor in Canada
Find out how you can apply for a study permit if you’re already in Canada as a visitor.
Problem with the online application
You may not be able to apply for your study permit online. For example, if you currently have visitor status in Canada and your spouse or common-law partner is a NOC C or D worker, you may need to submit your application on paper.