If you don't want to pay someone to do it for you here is how it goes:
Run power from the battery, from the amp kit, purchased from Best Buy, Walmart, or Circuit City, depending if battery is on the left or right side of the car, respectively to the trunk for power for the amp.
Replace the stock cd player with the one you purchased using a wire harness, found at Best Buy, Walmart, or Circuit City.
Inside the box for the amp kit, run the remote wire for the amp from the cd player's wire harness to the trunk.
At the same time run rca's from the preouts from the cd player to the trunk. Both of these wires will have to be ran on the opposite side from where the power wire was placed.
In the trunk, mount the amp away from any wires and the possibility or damaging the fuel tank.
Find a good ground and ground the amp.
Then connect the power, remote, and rca wires.
Find, buy, or build a box and mount the sub in it, and mount the box and then run the speaker wires to the amp.
Finally, tweak and tweak and tweak.
I may have missed a step but this should give you a general idea. It is not as easy as it read, there is a lot more minor things that must be done.
Remember, it is better to have it installed professionally. They warranty their work.
