Customizing Directory default theme

I am trying to customize the directory default theme/plugin……I did make the “search” box smaller…removed some of the text.

What I would like ,,,would be to add a right sidebar ….for adding advertising…..is this possible?….from admin on the now existing advertising page.Is there code I can add?

Anyways ,this is my design so far.. http://okanaganfoodie.com/

Any help would be appreciated…thxs