add a banner

if the banner is simply a linked image, add something like this wherever you want to show it:

<a href="https://linkurl"><img src="absolute_path_to_image" alt="" /></a>

you might need to edit one of the theme’s template files
(header.php or index.php or footer.php or sidebar.php or …)

https://codex.www.ads-software.com/User:Tomhanna/Adding_Ads_to_Wordpress