ok the video under is short but is complete
http://www.youtube.com/watch?v=zCo_ZHdqIAw
so your psu should ha two pci-e connectors you have two kind of pci-e power connector...one is a 6 pins and the other
is 6 pins + 2 , so check on your gpu if its a 6 pins or 8 pins power connector ( 6 pins + 2 )
depending on your psu , you need thoses connectors it look like that
http://techreport.com/r.x/psus-0907/pcie-connectors.jpg
or rarely a 8 pins power connector
http://i01.i.aliimg.com/img/pb/166/764/430/430764166_392.jpg
DO NOT MESS UP OR MIXED UP THE CONNECTOR ...EACH CONNECTOR HAVE A ROLE TO PLAY
pci-e is for gpu ONLY