How can I make a slider gallery span a window 100%?

How can I make a slider gallery span a window width 100%?

Here's the page with the gallery I would like to adapt: http://spiritoftheman.squarespace.com/index (if the link doesn't work, it is probably because I had to change the URL, but just assume it's any gallery that spans the entire canvas width.)

I would like it to look like the gallery on this page, window edge to edge:

http://www.squarespace.com/templates/?q=ishimoto%20blogging

Thanks for the help!