Using the SANYO LNS - T51 long zoom lens is easy. First, make sure your Christie DHD800 device is turned off. Then, carefully attach the lens to the device. When you turn on the device, you can adjust the zoom level from 1x to 1.67x according to your needs. Also, you can change the aperture between f/2.3 and f/3.2 to control the amount of light and depth of field. Remember to keep the lens clean. You can use a soft, dry cloth to wipe it gently. Avoid touching the lens surface with your fingers, as this can leave smudges. When not in use, store the lens in a dry and dust - free place.