Only One Visible Column

I am new to blogging, new to Wordpress and of course new to this theme. I have a modicum of knowledge of CSS and less of PHP but know enough HTML to get me in trouble.

This theme has all that I currently need and it appears it has all I will need in the future as well...so I want to make it work for me. But I am feeling pretty stupid at the moment because I cannot figure out why my layout only shows the middle column, not the sidebars. No links, no categories, not anything. I know this must be a setting that I'm missing. Please assist.