How do you hook up a sub-woofer and amp in a 2004 Mazda 3?

if you are keeping the stock stereo you have to get a rca converter(converts speaker wires to rca) and hook them up to the rear speakers. then run rca's to the amp, then run your power wire, ground, then the remote wire you will have to tap into the fuse box and find the radio fuse that turns off with your key, once you find that just tap into it and run the wire back to the amp.