Bolt it to the frame.
Positive post of capacitor is connected to the heavy amp cable. The ground terminal (or case) of the capacitor is connected to the car's ground or a ground wire that leads to the car's chassis. That's it.
your ground wire for the stereo is connected to the ignition wire of the car
yes
green
Might be bad ignition switch?? Check the ground wire as well. Check and clean if corroded: The Ground strap/wire from the frame to the engine The small ground wire from the battery to the body The Ground wire from the battery to the engine.
Negative - (Black) is Ground, Positive + (Red) is Hot. Ground wire goes to Negative (Black) it goes from negative on battery to engine for ground.
simple rule of car electronics: The black wire is ALWAYS ground
gound it put the wire in the ground of the car sterio
If you mean your gauges are going crazy, this is likely the result of a loose or bad ground wire. It could be the ground wire for your battery or any ground wire that is tied into the gauges.
to the frame of car
No, the ground wire should be attached to the green or bare copper wire. The black wires are typically live or hot wires and should never be connected to the ground wire.