Venting help pls and some other questions

OK so this is what i got goin on 3' 4' 7' grow hut tent k cool. right now using curly cfls 4 100 watt ones. now this is where i need help.i got a 400 watt mh sun system with built in ballast, that looks to only vent out from one side. Just bought a 4 inch inline fan a 4 inch carbon can and some 4 inch ducting. Now exactly where does everything go? is it ok to exhaust from tent to the outside of tent is it healthy to let the air just fillin in the room like that. Or do u vent it so that it goes out the tent and then comes back in, like a circle? kinda lost on this but i wanna start putting it togther. Im gunna search while i hope to hear some awsers thanks