I did not do the license in Ontario, I did it in AB but it should be similar. If you have a license from a country that has an exchange agreement with Ontario, you would just do an exchange. Since your US license is expired, it is probably not good for that but doesn't hurt to ask. If your other license is not from a country with an exchange agreement, that would mean you'd have to take the exam.
You can read about this at
http://www.drivetest.ca/en/license/OutOfCountryDrivers.aspx Because Ontario like many provinces has a graduated licensing program, you need to prove how long you have been driving before they will allow you to take the full exam and get a full license.
Before you take the written exam, study the book. Before you take the driving exam, make sure you drive carefully, don't exceed the speed limit, shoulder check and use your signals and you should be fine.