Use the adjusters on the monitor, the keys are on the side or the bottom, or in the case of a laptop their should be a way to adjust it in the contol panel/power options
My Computer
At a glance
Windows 10 Pro x64Intel Core i7 6700KGSkill TridentZ RGB 16GB 3600 16-16-16-36EVGA GTX 980 Ti SC x2