post box width

Hi

If you mean as wide as the cat photo, it appears you have theme options that let you change certain stylings

you want to make your content section 300 pixels wide

the css looks like this

body div#content {
margin:3em 200px 0 0;
}

add this to it width:300px; This is not in your style sheet. if you can’t find the place to do that, add this to the bottom of your theme’s style sheet.
body div#content { width: 300px !important; }