see the first pic on your 2nd post that little plastic box with the digital readout. power wire will most likely go there which connects to your battery
from the amp the earth cable needs to connect to a ground on the car (like a seatbelt bolt), and the red power cable needs to connect to the battery or distribution block that goes to the battery
had the same problem in my old supra. turns out it was my ecu playing up. wasnt sendin the correct voltage to my injectors and therefore werent pumping enough fuel and would cause it to stall at the lights and stuff.