To center the content, you can use the [segment] shortcode. Have modified the page accordingly. With the additional of little bit of code, it offers many benefits like –
1) Provide an option to create full width content (portfolio or gallery content which can span full width) instead of constraining all content to a 960px or 1140px centered grid.
2) Ability to set background color and background images to the segment.
3) Ability set parallax backgrounds with customizable parallax speed.
4) Ability to set background patterns, fixed backgrounds etc.
Pls go through the documentation on the [segment] shortcode for more information on how to use this shortcode along with arguments provided by the same. The sample data has many examples of this shortcode. Hope this helps