How long after I receive my immigration visa do I have to travel to Canada?

wasn't that in the information package you received?, why do you ask that here? lol

usually you have 6 months from the day your visa was issued. But you will probably receive your visa at least one month after that date( the day is was issued), mine i received it 6 week after it was issued, so i had less than 5 months to live for Canada.
Good luck