Hi, I just got into PC gaming so I am fairly new to all this stuff just so you know. I am installing a EVGA gtx 780 to my system. I have 875 watt power supply that I know can support a 780. My previous 680 took 2 6 pins. While 780 takes a 6 and an 8 (probably already new that). I know how to put the pins in for my graphics card but not for my power supply. Thank you for dealing with a noob.
You will need to get an 8 pin connection from the power supply, if you don't have one, you should be able to go from two molex to one 8 pin. Or 2 6 pin to 1 8 pin. You power supply will most def have an 8 pin connection though.