Centering wordpress website

Hello

Iam having some trouble with the wordpress template “MyStyle” from wooThemes. There is no option to chose between a boxed or stretched layout. The standard layout is stretched. The problem is that i want it boxed so i can put in my own background pattern.

Because there is no option to slect a boxed layout, I’m forced to adjust the css.

this is the body in the style.css file:
As you can see, I already added the margin and width attribute and this is the result: https://www.thomas-timmers.be/wordpress/

body {
margin: 0 auto;
width: 960px;
margin: 0 auto;
font-size: 1.4em;
line-height: 1.618;
color: #6c6360;
font-family: “Open Sans”, sans-serif;
-webkit-text-size-adjust: 100%;
-ms-text-size-adjust: 100%;
text-rendering: optimizeLegibility;
-webkit-font-smoothing: antialiased;
background: #fcfcfc;
}

Now my question is why the body is aligned on the left side but not centered? I tought that this (margin: 0 auto;) attribute should center the whole website.

Anyone know why the website is not centered? do I need to do something else or more?

Thanks!