There are 3 different layouts available for the Ambition theme.
The first one is the Content on the Left, and the Sidebar on the Right – http://demo.appfinite.net/ambition/layouts/cs/
The second layout is the Sidebar on the Left and the Content on the Right – http://demo.appfinite.net/ambition/layouts/sc/
The third layout is the Full width, Content only (No sidebar) – http://demo.appfinite.net/ambition/layouts/fwc/
You can select each of the layouts from the bottom of the page or post editor, and the Layout Selector should look something like this – http://i.imgur.com/VwN3YgY.png
If you want to set a default layout that works throughout the entire theme/site, then you can select the default layout on your Genesis Theme Settings Page – http://i.imgur.com/VhS46TR.png