I dont recall how but I know I installed one on my 07 Gallardo. Pull the trunk liner and install your fuse at the battery then I believe I ran it through a stock hole in the firewall (may have had to cut through an existing gromet but cannot recall. Then I think I ran along the driver side and then across the back shelf. I ran my speaker wires through the center console area and power wire around the side if I recall correctly.
It is pretty standard for running a wire. Pop your trunk liner out and then have a look. I dont recall anything out of the ordinary to install it.
I chose to mount my amplifiers upfront, and just run speaker wire to the doors and rear. It's much easier to run the speaker wires through the grommet on the driver's side firewall than to run a power wire from the front to back. Below is a front clip of a Gallardo with the two points, for left-hand drive and right-hand drive