Your post is unclear if you connected up the power to the new video card.
Recently I bought a (preowned but tested) Palit Geforce gtx 770 (4gb). Upon installation of what I am positive was completed correctly, my computer powers up (My LEDs and Fans on Case, CPU, and new GPU) but my monitor detects no signal. My leds on my headset and mouse turn on telling me my computer is booting but there is no signal on the monitor at all. I am positive my motherboard works but can not see what might cause this lack of function. Do I need to install the drivers for the card? More RAM maybe? Or is the card faulty?
Case: NZXT h440
GPU: Palit geforce gtx 770 (4gb)
RAM: Corsair Vengeance 1600mhz ddr3 (2x4gb)
PSU: Corsair CX600m
MB: Asrock z97 Anniversary