Motherboard graphics card issue?

I have a msi h81m p-33 motherboard and a nvidia gigabyte gtx 750 lowith profile graphics card the computer runs fine with just the motherboard and cpu but when I turn it off and put in the graphics card the fans spin and the hard drive starts up but there no response from the monitor I don't know if there's a power cord I'm missing or if there's something on the motherboard I need to do but any help would be appreciated