The procedure is outlined on a removable sticker placed on the ACP71 as shown, but since many of them look alike, and even may fit, it is possible to select the wrong power tip for your PC.
Inside the ACP71 lid Targus has placed another sticker showing the recommended tips by letter corresponding to the PC brand. Find the tip labeled for your PC that fits into the socket, snap it onto the ACP71 power cable (its keyed so you cannot reverse polarize it) and plug it into the PC power port.
Targus also has an on-line tool at http://www.targus.com/US/t/tip-configurator . Click on the “Yes” button from this screen, enter ACP71 for the model number, select the “Go” button, and follow the prompts.
Note, and this is important, the ACP71 is only for 19 VDC PC, and not for 12VDC tablets. If you are unsure of the input voltage of your PC, consult the manufacturer. Many times this is shown as the output voltage on the power supply included with the PC.
Finally, do be aware that the ACP71 supplies no more than 90W of power to the PC. If you have a 130W workstation PC for instance, the ACP71 cannot be used to power it.
For a video of the procedure, check out http://business.targus.com/t/b2b-videos-docking-stations .