Press the louver door frame against the window opening. Drill a pilot hole through the side of the window frame and into the window casing. You can place this first pilot hole anywhere along the window frame. Drive a screw through the pilot hole at a slight upward angle to hold the frame firmly in place. Continue to insert screws every foot all around the frame.
Place the louver doors on the floor with the side for the hinge facing up. The doors have hinge mortises, which are depressed, rectangular areas designed to hold the hinges, so the top surface of the hinges are flush with the door surface. Place a hinge in a mortise in a louver door, then drill pilot holes through the hinge's screw holes. Do the same with the other louver door. Drive screws through these holes to attach the hinges to the louver doors.
Get another person to hold a louver door in in the window casing to check its position on the frame. Use a pencil to mark the level of the hinges on the frame. Do the same with the other louver door.
Place the other half of the louver door hinge against the frame, aligning its position with the pencil mark you made earlier. Mark the screw holes of the door hinge on the frame and drill pilot holes at these spots. Align the door hinge with the pilot holes and drive screws through the door hinge and into the frame. Continue with all the hinges.