@Roanna... hi, re "what's the use of the single and insert sections? I added widgets to them on a test blog but they are not showing up"...
It's an extra area where you can add widgets, text, images, etc... Specifically the "single widgets" will appear on individual posts...
- above the post (single top)
- between the post & comment area (single insert)
- below the comment area (single bottom)
Also see my reply to a similar question at http://themeshaper.com/forums/topic/extra-widgetized-areas for a simple way to test it out for yourself.
Re "added widgets to them on a test blog but they are not showing up on the pages anywhere"...
Be sure you click on "save changes" when you add a widget to any area otherwise it won't be saved and won't show up in your theme.
If you need more help, please post a link to your blog so we can take a look. Later...