Audio Systems: One Sub - 6 channel amp, stereo head unit, factory speakers

Question
I took this from a car that was professionally installed and they had the amp hooked to the factory speakers and all. I just want to hook up the one 10" sub to it. I have the car wired for a system because i had one before but it was a different setup. Can you walk me through it? Ex. What wires need to be hooked up- which hookups i can ignore, etc.

Thanks

Bryan Settle

Answer
nowhere near enough info to even get started.  please answer all questions:

the year make model vehicle
The exact make model amplifer
The exact make model subwoofer
weather you've changed out the factory stereo (head unit) with an aftermarket (alpine, sony, kenwood, pioneer, etc) and if so what make model?
If you've added any other amplifiers.

So you want to use a 6 channel amp JUST for the sub and not for running any of the door speakers?

THANKS!