The ten toolbar buttons correspond to the ten parameters which define the view. The angle buttons, labelled xy to zw, can changed by dragging the dot around. When you let go, the fractal will update. By the way, the zw angle does work, you just can't see its effects until you rotate in some other dimensions first.
The four position buttons, x,y,z and w, can be clicked up or down to alter the view. They move the center of the screen by one third of the current image size with each click. Note that if you're looking at the Mandelbrot set, the x and y buttons scroll around the picture, but if you're looking at some other view, this won't necessarily happen. For example, if you're looking at the Julia set, the z and w buttons scroll, while x and y mutate the fractal.
Finally, the Undo and Redo buttons should be fairly obvious. You can undo as many times as you like. Note that undo also affects parameters such as color, not just position on screen.