I just ordered a couple 80 mm case fans from Newegg. I've never installed any case fans before. Is there a certain way that the air is supposed to flow? I've only got CPU and video card fans currently. Also, from the fan's picture, it appears that it has a 3 pin connector as well as a power supply adapter. Which one should I use? Actually, my system fan header on my MOBO is currently being used by the PSU and I don't see any other free headers.