It only has exhaust fans?
It shouldnt matter which you connect to. Also look around some more, there has to be a CHA_FAN1 connector somewhere. It will most likely be at the middle bottom of the board.
I'm remembering an article on Tom's about optimum airflow to find/reread. I'm wondering though ... if I have two case fans won't I get more airflow if the are running the same direction ... meaning both intake or both exhaust? Since there is no way to pressurize a case with all the grills I would thinktwo fans in the same direction add cfm ... in opposite directions they don't.