Check out the hot-linked areas on the left side Image menu.
I demonstrate how to use the circle, rectangle, and
For the circle you need the coordinates for the center of the circle and the length of the radius in pixels.
For the rectangle you need the coordinates of the upper left and the lower right corners.
And last, for the poly area you need as many points as you want in order to describe/enclose the area you want to be the linked area. The one requirement is that the first and last coordinate need to be the same in order to close the poly area.