To add a wide banner ad use the following code under any section where you want to show the ads.

<div class="big-banner-area themeix-ptb-2 bg-themeix">
   <div class="container">
      <div class="row">
         <div class="col-md-12">
            <div class="big-banner">
               <a href="https://themeix.com/get-ghost-hosting/"><img src="{{asset "images/banners/1.png"}}" alt="banner"></a>  
            </div>
         </div>
      </div>
   </div>
</div>

In that code use your own image link and the targeted url.