* Base on info supplied.
You will not be happy with the AC in place all year round.
If you bought the AC unit at Cdn Tire, than you did not get the best. If it is in a 102 year old window it is probably wood and not made to hold a AC unit all year round and collect moisture with will destroy the window frame and/or AC unit. If it is 5000 BTUs, then it is the smallest possible unit you can buy and will be running full blast all summer and you will not be happy with the results when the temperature goes above 25C. 5000 BTUs is OK for a room 10 x 12 but not more than that.
If it is not installed, then take it back to CDN Tire if you can. Buy a floor unit with a hose that throws the hat out the window with a tube. 10,000 BTUs is what you need. some units even have dehumidifying capabilities, and heat. they go for about $400-$450 at home depot.
* Get a ceiling fan, moving the cool or warm air around will help you stay comfortable.