Do you want to add the sidebar into no-sidebar site? Off canvas or toggle effect will be the good idea for it. So sidebar will not occupy the extra space from your content area. In this article I am showing how you will use the primary sidebar into off canvas sidebar. See the live preview at below:
Disabling the Blog Sidebar
Navigating to Appearance -> Customize -> Content -> Blog Layout and disabling the sidebar. Now sidebar will not appear on the site.
Adding Widgets into Primary Sidebar
Primary Sidebar is always enabled at Dashboard. So navigating to Appearance-> Widgets page and adding the widget(s) into Primary sidebar.