mac pro Mid 2010 Video not working through added HDMI port

I was given a mid 2010 macpro, this thing is maxed out with two solid state drive, 72gigs of ram, a bluray burner, plus a regular DVD burner. Also added are USB 3 and one HDMI output, it also has two DVI outputs. So I turn it on to install the OS, but I'm not getting any video I used the HDMI, I tried two different cables and neither works. Today I'm gonna try a DVI cable. So my question is this, do I need a driver for the HDMI cable to work? And if so will the DVI work, because they are on the same card from what I can tell. The USB 3 ports work cause the mouse I plug in is lit up. do I have to do something entirely different being the hard drives are blank. When I turned on the tower, I held down the control key to boot it. Maybe I'm over looking something, thanks in advance for everyone's help!