Disqus styling

I installed disqus as the comment system on my site as it is the preffered system I would like to use. However, because my theme was built upon the basis of the twentythirteen theme which is a full width theme, the disqus comments takes up the entire width of the site. I would like to know how I can limit the width of the diqus comments to something like 600px and have it aligned in the center of the page? The issue is that the sidebars overlap the disqus section.

Site: smattering.com.au

any help with this would be great,
Thanks!