If you work with Thematic for the first time, the most asked question will be, where are all these widget areas located?
You could go to the Widgets section in WP Admin and assign at least one widget to the 13 widget areas.
After installing a Gallery Plugin or a Forum Plugin you might want to remove the sidebar (Primary Aside and Secondary Aside) to gain more space for the plugin's output.
In my example for this task, I'm going to remove the sidebar from my page 'Forum'.
The major requirement for this and all other code snippets: You have to use a child theme
How to install a Thematic Child Theme?