hdmi mac

Whats up guys! I am new in this forum so, I don´t know how to post my problem (sorry). Well, I have an Asus P8H61-MX USB3 Mother Board and a Nvidia GeForce 9400 GT 1024 MB with Mountain Lion 10.8.4, this video card have a HDMI out. But the problem start when I am looking for connected my...