Depress the "On/Off" button on the front of the air conditioner to disable the appliance, and unplug the air conditioner's power cord from the electrical outlet.
Pull out the plastic foam seal located between your upper and lower window, and unscrew the filler panel's screws, using a Phillips-head screwdriver. There are three screws on the panel.
Hold the air conditioner with both hands, and have someone else unscrew the mounting screws located near the top of the air conditioner.
Pull up the upper window pressed against the air conditioner and have the other person grab the opposite end of the air conditioner to carefully pull and lift it out of the window.
Unscrew the leveling bracket on the window sill, using a flat-head screwdriver, and pull it off of the window sill. Slide the window down to seal the window shut.