One end of this jumper wire will be soldered to the diode at the top right. Don't worry if it touches the diode to its left as these two are connected from factory.

The other end of the jumper wire, will go to the input of the 12v regulator. There is a convenient pad right next to it you can use.

Connecting to the output of the 12v regulator: If you use a good quality, regulated 12v power supply, you can actually connect this end of the wire to the OUTPUT of the 12V regulator for lower thermal operation (located at TP14) however,

by using the input pin as indicated here, you will be able to use a power supply higher than 12v, and also, the 12v regulator will serve as protection in case anything goes wrong with your power supply or for when someone accidentally connects an old 9V AC power brick to your drive.