This is the default layout for most webpages. You have your main content on the left with a sidebar on the right. The reason for this layout is it’s easily recognizable by users since most websites follow this style of page format.
In order to have your page follow this layout theres actually nothing extra for you to do. When you are editing or creating a page in the backend of your site, on the right hand side there are options to choose from under the Page Attributes and under Templates there is a select dropdown list and it’s automatically on the default page layout.