I can get part of the answer then I get stumped.

find the center and radius of the circle, Write the standard form of the equation.
(4,3)(1,3)
to get center:
(1+4/2, 3+3/2)=5/2,3
answer:5/2,3 for center

radius:
then i am stuck

I assume the coordinates given are the endpoints of a diameter.

In that case, you have the center.
the radius (duh) is half the diameter: 3/2