Nah, forget the drawing. I'll just explain.

Okay, you need wires that go from the amplifier (in the trunk) to the front speakers (in the dash or the doors).

Well you could run your own speaker wires. And an audiophile will tell you that you should run your own super-expensive wires because they'll give you better soundstaging or something like that, but let's ignore that BS for a moment and assume that just any old wires will do.

Let's also assume that your car has an ordinary stereo system where the head unit supplies the power (i.e., it's not a Bose or Infinity system with an extra amp hidden somewhere).

Let's also assume that your car is an ordinary sedan, with four speakers: One each in the driver and passenger side front doors, and two in the rear "deck" behind the back seat passengers' heads.

Well, the car itself has four sets of perfectly good wires that run to those speaker locations. They run from the radio connection harness in the dash, out to the front doors and also back to the rear speakers, connecting in the trunk space.

Since your amplifier is now in the trunk, what you do is run one set of speaker wires from the amp directly to the rear-deck speakers. Now suddenly the factory wires that run from the dash to the rear speakers aren't used any more...

So, plug your front-outputs from the trunk amplifier into the now-unused rear speaker wires. And up inside the dash, right there on the factory wiring connector, run short wire loops from the rear speaker connections to the front speaker connections, and now you've got a wire run to the front speakers from the trunk.

If you're particularly slick, you can do this all with nicely-made adapter connectors instead of splicing into the wires directly. So if you ever sell your car, you simply unplug everything and plug the speaker wire connectors back to the way they were from the factory.

Make sense?