Tulip is a powerful yet versatile Graph Visualization Framework. Go have a look at Tulip's website.
Download and install are fully documented on Tulip's website. From now on, I'll assume you are using Tulip on Windows (and have installed the latest release (using the autoexec install bundle).
Tulip will also be available from computers accessible in your classroom. From now on, it is assumed you have access to Tulip and that you are able to launch it and use it.