Here are some step by step examples you may find useful. If you are unfamiliar with how to build a system, you may want to look over these tutorials first.
You can build and wire together as many of these examples as you want on a single system - just be sure that your IDs for your devices are all unique. You can also create multiple systems on a single computer. Just startup the Virtual Wiring application multiple times, while assigning a different port number each time.