A common mistake.
And will be down to what video output is set as default in the bios.
So first try plugging the video cable from the monitor into the Pci-e graphics card or the on board video port found on the motherboard.
Once you find the correct one that does display a picture, you will need to go into the bios of the board and change the default graphics output device.
So in your case set it to Pci-e in the bios list. (The Gtx 760 card).
Save the settings before exiting the bios.
And swap the video cable from the monitor to the back of the Pci-e Nvidia graphics card.