1.Click your shape to select it.
2.Move the mouse cursor over the point that you want to drag. This should be a point on the perimeter of the shape, not the sizing handles.
The cursor changes to 
3.Click and drag the point to its new position.
4.Release the mouse button.
See also
To add a point to a shape or line
To remove a point from a shape or line
To open closed shapes and lines