Nikon D90 picture control?

I just bought a Nikon d90, I only used film SLRs until now so some features are new.
When I go to picture control it doesn't let me go on it for some reason, saying that the settings i put won't allow it,
I didn't do anything! How do i unblock this?

Usually an error of that sort is due to the fact that you are on auto mode

go to "M" on the dial and it will be completely manual. That should get rid of any dialogue saying "you can't do this because this setting does not allow it" or something like that

Set the mode selector to any of the PASM modes. Auto should be avoided at all times. Program mode is like auto mode, however, you choose when you should use flash and you can apply exposure compensation.