How do you fix a computer screen if nothing shows up ?

I have a lap top computer that works, except for one thing – The screen does not show anything !

It turns on fine, but the entire screen is white and nothing shows up.

I want to know also how much something like would would cost to fix it ?

It fell on the ground, on it’s flat part, so there is a little small crack in the middle of the screen when you first open it up.