If you're not a NetBSD developer, tell us your OpenID.
To see what Markdown does with your input, there is Dingus (it's an external site) which also has a nice cheat-sheet for the Markdown-syntax.
Feel free to use the graphic chart as an example for your page. You are not forced to follow its layout, but it can help you to quickly design pages so that they look better integrated with the rest of the wiki.
To practice, you can play in the SandBox.
Your first page
Write whatever you like, wherever you like. It's a wiki! Have fun. :-)