Trying to style current list item

The theme I am using is Divi

I’m reading this article https://premium.wpmudev.org/blog/how-to-highlight-the-current-page-when-using-wordpress-navigation-menus/

I am trying to get the background to remain activated for the current page I am on. I am dealing with multiple menus. I can get this to work, but it applies the highlight to all menus, not just the one in my sidebar.

Do I need to add a class to each menu item? The name of the menu is Free Course

If you need to get into the site to see more, let me know.

Thanks,

ME