Depending on your province of residence and the jurisdiction of your legal training, you'll either need to take some foreign lawyer equivalency training and a professional legal training course and pass a licensing exam or you'll need to go back to law school for a while. Paralegals are similarly regulated.
Unless you are moving from a common law jurisdiction with close relationships to Canada, moving here to be a lawyer or paralegal is difficult and expensive.
Absolutely do not attempt to practice law without a license.