Make my theme wider

I want to widen my theme a little bit wider than what it has to offer, how can i go about this, i seriously need some help as i am no good with CSS

http://harbor-cleaning.com/

Hi!

There are several css files: style.css located in the directory of the theme and the others inside /css folder. Inspecting the page you will be able to find the line and the file you have to edit. Unfortunately, we don't provide such kind of services.