posting ads on the upper right part of the website

i would like to know how can i post the advertisements on this location:
https://www.dropbox.com/s/12hq9h0qlcxkjqo/Image%201.png?dl=0

the theme that we are using is this;
http://themeforest.net/item/realia-responsive-real-estate-wordpress-theme/4789838

* i asked them already how to do this, they told me to ask
developers for a more accurate estimate