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