The sidebar's location is controlled by your WordPress theme. If you're not happy with the sidebar's position then you may be able to change it using the theme settings.
Many of the best WordPress themes let you choose between different layouts. Often, this includes showing the sidebar on different sides of the screen.
To see whether your theme has different sidebar layouts, go to Appearance » Customize in the WordPress dashboard. Here, look for any settings labelled Sidebar or similar.
Simply click on this option and look for any settings that allow you to change where the sidebar appears on your site.
After making your changes, click on the 'Publish' button to make the new sidebar layout live. If you can't change the sidebar's location using the built-in settings, then another option is to create a WordPress child theme.