Do you already have a search form script, widget, or plugin that can do this, you just need it placed into the theme?
If not, you might find something here that will work: https://wordpress.org/plugins/search.php?q=search
If yes, on the free version, you’ll need to use a child theme (https://startupwp.com/topic/child-theming/) and the pro version you should be able to use the body scripts area in your theme options (https://startupwp.com/topic/setting-your-themes-options/).