How to move your content over with CSS

Hi guys,
I’m reaaaaaaally green when it comes to CSS. I have figured out a lot of what I’m trying to do, but it appears that I cannot figure out how to move my content over so it sits in the center of a page. It stays slightly right.

Here is my page for example: http://triciavictoriaphotoblog.com/ashley-mich-trash-the-dress-pt-2/

My theme is Spun.

Thanks for your time!

Tricia