How's she gonna get into the cockpit to shut the engines down, when the door's locked?
Harsh language?
Seriously, MS Flt Sim will give as much info as you are likely to need.
in almost every modern airliner type, simply look for a red, T-shaped handle in the panel above the pilots, and pull it. There is one for each engine.
Unless it's a 737 which means the Fire handles are on the pedestal just behind the throttles levers.
Oh and on an Airbus they are push buttons.
