Twenty Fourteen Theme CSS Customization

I’m trying to make the twenty fourteen theme wider but I’m am having issues achieving that.
I tried using this forum to figure out how to make it wider but the solution is for wordpress.com themes.

http://en.forums.wordpress.com/topic/twenty-fourteen-theme-css-customization?replies=10

For some reason the image comes out small but the text is the proper width.

This is the site I’m having trouble with:
http://www.akibajin.com/

https://ww.wp.xz.cn/plugins/css/