Follow these steps to properly adjust your monitor.
Turn your monitor's Picture control to minimum to display a black picture.
The minimum setting of the Picture control causes the picture content to disappear entirely. If your monitor's picture cannot be made to vanish, then you will have to arrange to display a picture that is substantially black (for example, by activating a screen-saver).
Turn your monitor's Black Level control to adjust black correctly.
Turn the Black Level control to the balance point or threshold. The threshold is low enough that a black area of the picture emits no light, but high enough that setting the control any higher would cause the area to become a dark gray.
Turn your monitor's Picture control to adjust the brightness level.
Once the black level is set correctly, the Picture control can be adjusted so that a white signal produces the appropriate level of brightness. There is no proper setting of this control; it depends entirely on your preference.
Avoid setting your monitor too bright. Excessive brightness can increase your sensitivity to flicker, reduce the contrast ratio of the picture, and defocus the electron beam of the CRT, resulting in poor sharpness.