How do I add the Widgets menu using “Hello Theme” for Elementor?

To enable the Widgets menu item in the WordPress admin menu, add the following code in your functions.php file

if (function_exists("register_sidebar")) {
register_sidebar();
}

You will then have the Widgets menu available to you, you can then assign Widgets to the Sidebar as usual in Appearance > Widgets.

Note: This may cause a warning in WordPress 5.6. My local version was fine. My server version had an error!