Monetizing Drupal Site

[mediamonster]

You don't have to worry about it. Many advertising platforms (such as adesnse) provide a piece of code which you will just have to put in the HTML of your site and it will show ads on its own. And also now-a-days ads are responsive so they will adjust themselves according to size of the screen what the user is viewing through.

Its just same as wordpress or any other CMS.