Wide image over content

Hi there,

I would like to place an image before the content comes. The image should be full width, the content boxed.

Now I have placed a cms-code box upon the cms-content. I put this code in the cms code:
<?php if (has_post_thumbnail()) { if (has_post_thumbnail()) {?> the_post_thumbnail();
}
?>
to show the selected post image or featured image from the wordpress site in it. But the image won´t be displayed.

Can you help me to get a solution here, please?
Many thanks,
Antonio