Para sacar una visa a Canadá debes hacerlo desde tu país de residencia:
First Step: The foreign national must first submit a visit visa application to the responsible Canadian visa office in the country or region where they reside.
http://www.immigration.ca/en/canada-visa/canada-visit-tourist-visa.html
Si tienes residencia americana (Green Card) no necesitas visa sino un eTA
Venezuelan Lawful permanent resident of the U.S. with valid Green Card
You need an eTA to visit or transit through Canada by air if you are a lawful permanent resident of the U.S. and have a valid alien registration card (Green Card).
Note: you will need a passport from your country of nationality to apply for an eTA.
http://www.cic.gc.ca/english/visit/visas.asp