If you see a black box with an X in it, then you have the correct plugin. Hitting the little x-button should make the X in the window spin around the horizontal axis. ( In Internet Explorer you may have t o click twice when you first use it.)  If you drag with the left mouse button depressed, you should be able to move the X around.

The plugin will work on a PC under windows in the student labs. Mozilla is prefered over Internet Explorer, but only because the X-button must be hit twice the first time it is used to have an effect.

It will be unlikely to work on Linux, or MACs.

If you are good at loading plugins, you may download onto your own machine from. We can't help you with this. Don't spend time on this if it doesn't work and don't use it as displacement activity for getting on with the exercise.