how to add sub-pages to wiki


In looking through the documentation and trying out the wiki plug-in, I'm having a hard time adding sub-pages to a wiki. What's the recommended way?

Also, I'm using the Twenty Twelve Theme and when I go to edit a wiki page while in the site (not from the dashboard), I end up having three editor windows on the same page - two bare-bones ones, and one more that is embedded within the site.