I am new in Graphics but my Art is strong. How can I use my Art in Graphics and what I have to do for it?

Graphic is also Art. Its good if you are proficient in Art. You do manually Art, Graphic is a digital Art. 

Try to learn the Graphic software i.e. Adobe Photoshop, Illustrator or Corel Draw,3D Studio Max etc.. And apply your art in these software to be a proficient in Graphics.