There is no proper way to use an evaluative metre (or matrix as it's called on Nikons). The amount of calculation work the camera does in body based on all sorts of factors like focal length focus point, focus point position on the frame just to name a few makes knowing reliably what the camera will do difficult.
It should also have a spot metre and or a centre weighted average metre. Both of these metres try to turn the picture to middle grey (18% grey or colour #888888 on the 24 bit RGB set) A spot metre takes a reading only from the dead centre (if you have one) and the centre weighted gives about 60% weight to the middle area of the frame.
As for how to use this information, this varies wildly depending on a given situation.