By default, the Hello Theme does not call the WP sidebar functionality. You can create a child theme and add a snippet of code as shown here to the functions.php file of a child theme.

If you would like to use the WP sidebar widgets along with Elementor widgets, without using code, you can do so by creating a sidebar in your Single Page, Single Post, and Archive templates in the Theme Builder. These templates will allow you to feature a custom sidebar on your site for each new page or post.