hey leon, do you have a dualshock 3 or something? Im not too sure about them, but with the other ones all you do is solder either the leftmost leg of the sixaxis plug thing (i can post a image if it helps) or you can alternatively solder to the solder point TP11 on the other side - for +ve of the LED. For the -ve side just solder to any ground connection, its common to solder to point 5 on the bottom right of the controller.
Post up a pic of your board, I might be able to highlight where you need to put solder points to. Make sure to photograph both sides.