Centralise content of full-width template

Hello! This is the page that I would like to tweak: http://thinkauthentic.com/about/. I am using the full-width, no sidebar template and have managed to reduce the width of the content by using the following:
body.full-width .site-content {width: 70%;}

Anybody knows how to make the content align (horizontally) in the middle of the page? Thanks in advance!