Hope this kinda helps...
Well to start with you really need an amp.
The amp runs to to head unit and connects via the remote chord (look in your radio manual to find out which one this is (normally blue irrc)) and it also connect directly to your batter to power it. (you can buy a wiring kit from halfrauds)
The sub then connects to one of the outs on the amp, i.e one + and one - with some DECENT thick speaker wire
I screwed a small wooden plate to the side wall of the the boot and then screwed the amp to that. (All the wires connecting amp to radio and sub to amp in the boot are hidden behind that bit of wood) nd the sub just goes in the back left corner of my boot
The wires that have to run inside the car are easily hidden as they can go down the corner of the back seats and then under all the interior plastics i.e the rear door cards and then under that strip of plastic that runs along the bottom of the car, these all come up easily enough.
I holy my sub in place with some of the super strong velcro you can also get from halfrauds, a lot of people dont recoment this but i find if you screw it to the base of the sub with some very small flat screws it works extremley well and sticks straight to your bootfloor.
Hope that helps.