These are the important settings when you navigate to Admin > Genesis > Theme Settings:
(note: this moved to the "Customizer" as of Genesis 3.0.0+)
This Default Layout sets the default layout for all posts and pages, which can still be overridden on each individual post. Make sure Screen Options > Layout Settings is enabled on the post editor page:
Genesis comes with 3 primary layout settings that work for 99% of websites - content left sidebar, content right sidebar, and full width content.
The most popular practice is to use the right-sidebar as default, which allows you to put in calls to actions for newsletter signups, ads, badges/logos and call attention to something you find important, across the entire site.
The left sidebar is identical but is a little-used layout option. Do not use this unless you have a very compelling reason.
Full width layout
Full width content is great for special landing pages where you want to keep the focus entirely on your content. This is commonly used for sales pages / landing pages for courses and ebooks that you may sell.
The Genesis Theme Settings page controls only a portion of the overall website layout and design. For more specifics, see our How to Customize Your Theme guide.