UPDATE: THE NEW TV LOCATION IS IN THE CHASM GHOST RAY THE RIGHT WALL OR SEE MY NEW TV LOCATION POST
To get the TV you must have Ghost Ray. Then head to Farthings Meadow. There are two trees together, close to the goal posts. Ghost Ray the darker one. You will see the TV in the top of the tree. Click it!
To get into the Secret TV studios you must ZAP a tv, any TV will do. There’s not much to do there and there’s usually no one else there.. But you gotta check it out anyway.