Place the inside portion of the door handle into the rectangle hole cut into the inside of the door. The inside portion of the door handle does not have the main lock connected to it. However, it will have a smaller lock, called the "night" lock attached to it. The night lock goes towards the bottom of the door. Hold the inside portion of the door handle in place with your hand.
Place the outside portion of the door handle into the rectangle on the outside of the door. The latch on the lock must face the direction the door will slide. If it does not, loosen the screw on the latch and rotate it to the correct direction. Tighten the screw before placing the lock into the door. Hold both sides of the lock with one hand.
Thread the two screws that hold the two sides of the lock together through the inside portion of the door handle. Tighten the screws with a screwdriver.