I have quadrangle with coordinates x,y (3, 4) (2, 5) (8, 3) (4, 2), can someone explain how to use them in this formula

Centroid - Wikipedia, the free encyclopedia to calculate centroid.

I know how to get the area, but I have no idea how to use these coordinates in this formula. My english my not be perfect, in this case by quadrangle i mean an irregular figure where every angle may differ.

Thank you