This is the best picture of my grow tent that I could find for you:
Basically what you want to do is extract the MJ fragrance in the tent, and exhaust fresh air OUTSIDE of the tent. Because if you just have a fan blowing hot air out of the tent, then its going to be hot air that smells like MJ.
Hook your filter up to the INTAKE portion of the fan. The filter will absorb the odor and exhaust it outside of the tent.
I have another fan hooked up to my hood, that intakes cool, fresh air from outside the tent, blows it through the hood to cool the bulb, then exhausts the semi-cool air into the tent. So the lifecycle is repeated... Cool, fresh air gets brought into the tent, which cools the bulb and gets re-circulated throughout the tent. The hot and fragrant air is absorbed by the activated charcoal filter at the top of my tent, and exhausted through a hole in the side.
Just make sure everything is sealed properly, and that there's no suction loss. If your filter isn't picking up the odor, you have a loss of suction or a shitty filter.