So that I can use the primary sidebar as widgets and secondary sidebar as customize lists. Here is the original sidebar.php.
In order to activate the widget sidebar, we need to register both primary and secondary sidebar in theme functions file, functions.php, as below.
Lastly, we need to change the WordPress theme layout, layout.css. Both sidebar elements are right floated. Secondary-side element is cleared to right. So that it can drop below right floated primary-side element.