you need to upgrade your graphics card which supports dx11, and your games must support dx11 too. Many famous games like BF3, Skyrim, Crysis 2, etc supports dx11.
As for the card, cards that support dx11 are:
-ATi HD 5000 series
-ATi HD Mobility 6000 series
-AMD HD 6000 series
-AMD HD 6000M Series
-AMD HD 7000 Series
-AMD HD 7000M series
-nvidia 400 series
-nvidia 400M series
-nvidia 500 series
-nvidia 500M series
-nvidia 600 series
-nvidia 600M series