header ad?

I’m not familiar with this template. I’d say the first thing you might want to do is give yourself a little bit more room for ads, by turning off the search feature in the header. I’m not sure if there is a checkbox in the admin panel for turning the search on/off or not.

And most templates are different with regards to the back-end features. This theme may simply not have a place to easily add-in such code for something like Ad Sense. You might look for an ad-sense plugin that could help you.