You can start filling out the application forms before you get married but you can not apply for anything until then unless you live together as common law partners for 12 months, then you can apply to sponsor him as such.
It is not so easy that you can just marry him overseas and then you both get on a plane to Canada together. After getting married, you need to apply to sponsor him for PR and that can take months and in some cases over a year. As a Canadian, you may sponsor him even if you are visiting him in Chile at the time. However, if you are exclusively living in Chile, you would have to provide proof that you will be moving to Canada when he gets his PR. Him coming to Canada with you would depend on him getting a visa to enter Canada.