Remove the supplies from the installation kit. The kit has a top mounting rail, foam window gasket, window sash foam seal, top mounting rail seal, and a left and right accordion panels. The kit also includes four small screws, six longer screws and 1 window locking bracket.
Remove the backing from the top mounting rail strip. Place the top rail on the sticky side of the strip so the back and front sides are flush together. Place the top mounting rail and seal on the top of the air conditioner towards the front of the unit. The smooth side of the rail will face the front and the rail slide will face the back of the unit. Line up the screw holes. Use the four small screws to attach the rail to the air conditioner.
Open the right and left accordion panels, by holding the hard part (end) and pulling gently on the accordion panel. Slide the accordion ends in the guides on the right and left sides of the air conditioner.
Measure the inside of the window frame. This is the length you need to cut the 2-inch wide piece of wood. The wood thickness must be 1/2 inch higher than the frame of the storm window. For instance, if the frame lip is 1/2 inch, the piece of wood must be 1 inch thick. Place the wood piece in the window frame. Secure with one nail on each side or use duct tape if you don't want to nail into the vinyl window frame.
Open the window high enough to fit in the air conditioner. Remove the backing from the window foam sash seal. Use a scissors to cut the piece to fit the window length. Press the seal firmly on the bottom of the window sash. This is the part of the window that closes down on the air conditioner.
Place the unit in the window. Hold onto the unit and close the window down on the unit so the window closes in back of the top mount rail. The window sash will be on the backside of the rail and will hold the unit in place. Let go of the unit. Measure the distance from each side of the unit to the side of the window. Move the unit left or right so it is centered in the window.
Pull the hard sides of the accordion panels to the sides of the window. Use five long screws to secure the accordion panel to the window. There is a hole on the bottom and top of each panel on the hard side against the window frame. If you have vinyl windows and don't want to make screw holes, use a colorful duct tape to hold the panels in place.
Cut the foam window gasket the length of the window. Push the foam down in the gap where the bottom of the window meets the glass of the top window. Since the bottom window doesn't close all the way, the foam seals the opening to prevent air from escaping and bugs entering.
Use the window locking bracket to secure the bottom window from opening accidentally. Attach the lock to the window and frame using the last long screw. If you have a vinyl window and don't want to make a hole, measure a piece of wood long enough to fit between the top of the open window and the top of the window frame. Place the stick in the window and use a piece of duct tape to secure it in place.