hi,
I am no expert but the following code works for me..
Create a new page via ftp and name it.. page-fullwidth.php and place it in the themes folder.
<?php
/*
Template Name: Full Width
*/
?>
<?php
get_header(); ?>
<?php while ( have_posts() ) : the_post(); ?>
<?php get_template_part( 'content', 'page' ); ?>
<?php
// If comments are open or we have at least one comment, load up the comment template
if ( comments_open() || '0' != get_comments_number() ) :
comments_template();
endif;
?>
<?php endwhile; // end of the loop. ?>
<?php get_footer(); ?>
Then when you create a post or page simply select the Fullwidth Template option.