First find this segment in your coding:
#outer-wrapper {The "width:692px;" line indicates the width of your header and post/sidebar sections together. You can change 692 to 800 (to fit Kristen's example) or desired width. I've managed with a 900 width, but that might be pushing it.
margin: 0 auto;
border: 0;
width: 692px;
text-align: left;
background: $mainBgColor url(http://www.blogblog.com/moto_son/innerwrap.gif) top right repeat-y;
font: $bodyFont;
}
Now find this segment in the coding:
#main {
width: 400px;
float: left;
word-wrap: break-word; /* fix for long text breaking sidebar float in IE */
overflow: hidden; /* fix for long non-text content breaking IE sidebar float */
}
The "width: 400px;" indicates the width of the blog post area (not including sidebar). You'll want to widen this too, or you'll have a big wide area in the middle of your blog. I would suggest a width of 528 in Kristen's example, but you can play with different numbers to see what works.
Hope this all makes sense. It's a little challenging to try to explain. :)