First you need to open the TV and gut out the original electronics including the large and heavy screen.
CAUTION: A TV is a device that stockpiles large amounts of high voltage. BE INSULATED DURING THE ENTIRE DECONSTRUCTION PHASE TO AVOID LETHAL ELECTRIC SHOCKS!
CAUTION: The picture tube is made of glass and has a high degree of vacuum inside. HANDLE IT WITH CARE AND WEAR EYE PROTECTION. If it breaks it will implode and scatter shards of glass everywhere. If you do not know how to render it safe, take it to a professional TV-repair technician for disposal.