How to display adsense ads in place of default ad banner

Hello Kalle,

You can create that option using child theme https://codex.wordpress.org/Child_Themes.
You just need to alter this hook
add_action( 'supermag_action_header', 'supermag_header', 10 );
This hook is present in acmethemes/hooks/header.php on line number 291 of current theme SuperMag version 1.1.8.
And thank you for using our theme. Please follow this documentation for using theme SuperMag http://www.doc.acmethemes.com/supermag/, it may solve your other problems too.

Thanks