Instructions
Turn on the PS3 you want to connect the PS3 controller to.
Plug the mini-USB end of your controller's USB cable into the controller's USB port above "Sony."
Connect the other larger end of the cable into one of the USB ports on the front of the PS3. The four lights on top of the controller flash for a few seconds. After the lights stabilize, the controller has successfully been paired with the PS3.
Disconnect the USB cable from the PS3 and controller to begin using the controller wirelessly. Alternatively, leave the cable connected to use the controller while it is also charging.