Click on the Curve menu to choose one of the associated curves. Then click on the diagram to choose a point for the involutes, pedal curve, etc. You can then move the point around and watch the associated curve change.
For the inverse (wrt a circle) click the mouse and drag to choose a centre and radius. You can then drag the centre of the circle
Use the buttons on the right to move the graph or the ones in the middle to alter the scale. The buttons on the left can be used to alter the value of the parameter a. The two inc buttons alter the rate at which you can vary the parameter.