If you like to tinker, please feel free to follow the instructions below, otherwise, you can submit a request for the banner ad and we can implement the banner ad for you.
These instructions work for Pro papers on a custom domain and will add an Adsense leaderboard ad (728X90) below the navigation menu.
1.) From your Paper Settings Dashboard, click Layout & appearance, Look & feel, then Custom Header. You should then see your Custom Header HTML editor.
In the Custom Header HTML editor field, you can add the following code, but replace "<!-- Adsense Code -->" with your banner ad's code and a value for XXX.
The "XXX" depends on how far down on the page the ad needs to be placed. As a general rule of thumb, take the height of the paper's banner, and then add 66px.
<div style="width: 720px; position: absolute; top: XXXpx; left: 50%; margin-left: -364px;">
<!-- Adsense Code -->
2.) Then you need to add the following code to your CSS editor. To access your CSS editor, from your Paper Settings Dashboard, click Layout & appearance, then Look & feel, then Custom CSS to access your CSS editor.
Some papers may be a bit tricky in finding the right "XXX" value, so feel free to let me know if you prefer I edit your paper directly.