I think you need to have a much clearer understanding of automotive wiring, or find someone that does before you burn up the car.
That aside, one needs to diagram out the modifications to the electrical system, make a few calculations, properly size conductors, make provisions for over current protection (fuses), and then install it.
Keep in mind the bulkhead connector when new could not handle much amperage for any length of time; perhaps around 25 amps continuous. Any continuous high amp loads have to bypass the bulkhead connector, and be feed from a secondary power distribution point added to the factory electrical system. Also a charging circuit bypass, along with a higher capacity alternator will need to be installed to handle the increased load of a 200 amp sound system.