Increasing theme width

Does anyone know how to increase the overall width of a theme? I want to get rid of the side of my blog that's just empty space on the edges or at least reduce their size if you know what I'm talking about. I want both the sidebar and content column to be bigger.

 

You will have to edit style.css file which is generally defines your theme layout and look.

 

Thanks so how do I do that?

 

rodog, if you can post a link to your blog/site with the theme in question being used, I'll be able to tell you how to do it.