need help installing amp in 14 malibu ltz

Power wire needs to route through the firewall on the driver's side.  Each year/make/model is unique so you'll have to find a spot that is clear on both sides of the firewall.  Maybe group with other wires, if space allows. 

Ground needs to go to bare metal and as close to the amp as possible.  Grounding location importance is somewhat determined by how much power you're looking to pull.  The floor is always a save location to use, just be careful of what's under the floor in that spot.

Maybe someone with the same car will chime in.