Featured Graphic Missing on Post

Hello,
To show featured graphic post, you need to add this:

if ( has_post_thumbnail() && is_singular('post' )) {
the_post_thumbnail('');
}

in functions.php within the <div class=”banner”>

What can I do to make sure the featured graphic is posted on the blog post?

Go to Appearance->Editor-> functions.php and edit, So the whole div will look like this once you’re done:

<div class="banner">
		<div class="wrap">
			<?php
			if(is_front_page()) {
				lifestyle_get_home_banner();
			} elseif ( !is_front_page() && get_theme_mod( 'lifestyle_header_home' ) ) {
					echo '';
			} else {
				// get title
				$id = get_option('page_for_posts');

				if (( 'posts' == get_option( 'show_on_front' )) && (is_day() || is_month() || is_year() || is_tag() || is_category()  || is_home())) {
						lifestyle_get_home_banner();
				} elseif(is_home()) {
					if ( has_post_thumbnail($id) ) {
						echo get_the_post_thumbnail( $id, 'full' );
					}
				} elseif ( has_post_thumbnail() && is_singular('page' ) || has_post_thumbnail() && is_singular('post' )) {
						the_post_thumbnail('');
				}
			}
			?>
		</div><!-- .wrap -->
  	</div><!-- .banner -->

I recommend you not to edit Lifestyle directly, since it is child theme of Omega but still create a child theme of Lifestyle http://codex.wordpress.org/Child_Themes to work with.

A child theme of a Lifestyle also helps to keep any customisation during the next upgrade.