Many of the web pages on the Builder come with page layout options you can choose from to customize the look of your website. When you click on one of your pages in your Builder, the first option you'll see is the layout that is currently chosen, and gives you the opportunity to change the layout.
To change your layout, click on the change button and you will see all the page layout options available for that page type. Click on the page layout you'd like to use, then click on save changes.
The only page types that do not have multiple layout options are drop down menus, embedded link pages, external link pages, and rss feed pages. This is because these page types link to other pages and content.