Adding content to the sidebars of your site is done using the widgets functionality. Widgets are pieces of content (text, images, blocks, etc.) that you can set to show on one or more pages in available widget areas like the left/right sidebars or above/below the main page content.
In this example, we'll add a sample reusable block (we named Sidebar Right Content) containing content we want to add to the Sidebar Right widget area.