Get on your hands & knees in the passenger footwell & stick your hand up behind the glove box, a couple of inches up you'll feel the main loom, trace that back towards the front of the car until you hit the firewall, it will go through a big rubber bung into the engine bay. Feed the power through there.
Alternatively, pop the hood have a look down from the coolant expansion tank & slightly to the left & you'll see the other side, it's a bit easier to get at & you can see what you're doing!

After that, undo the trim in the passenger footwell & the two scuff plates inside the doors & feed the wiring along there & under the carpet beneath the back seat & into the boot.
Hope that helps!
