Nobody seems to be answering here, which is probably because we're all a bit confused.
If you really mean 'TV' then I can't really understand what it is that you're seeking to do. TV sets are designed so the picture fills the screen, so Ican't see how it could be too big. (If that is what you mean though, please explain your problem further and tell us the make and model of your TV set).
If you're actually referring to your computer monitor though, and it's the display from your web browser which is too big, press Ctrl and - together to make it smaller or press Ctrl and 0 together to get it back to the default size.
If I've completely missed the point, because you're referring to something else entirely, please explain further.