Where can I find this line of code?

wrap-content is the main container, the same container that show pages content, post content and is a core part of code. There is no reason to edit wrap part and risk to break the whole site, cause all you create with pages/post edit/visual composer are inside wrap-content

In your child theme’s functions.php file, use this code

add_action('kleo_before_main_content', 'inject_adsense', 10);
function inject_adsense() {
    //your adsense code here
}

Here is a list of hooks: https://archived.seventhqueen.com/documentation/kleo#hooks

The inject code does work. So perhaps you are not inputting your adsense code correctly. See if I change the code I gave you to inject a “Hello, World” message, it does display on the site.