Adding thumbnail code to The Loop

First, I am very green and know no coding, just what I’ve learned from youtube videos to fix problems. I just added a blog page to my static homepage website (www.restorationworkshop.net). I made my first post but am now running into the problem of the Featured Image not showing up. In searching through posts with similar problems I’ve already enabled Feature Image in the Screen options and added add_theme_support( 'post-thumbnails' ); to the theme’s function. I believe next I have to add <?php the_post_thumbnail(); ?> to The Loop, but I have no idea where to add it. Below is what appears currently.
The background on the blog page also isn’t the same as the other pages and I can’t even begin to think how to fix this. Not as critical as the Featured Image, but looking for help on that as well.

<?php
/**
 * @package WordPress
 * @subpackage Enterprise
 * @since Enterprise 1.0
 */
?>

<?php /* If there are no posts to display, such as an empty archive page */ ?>
<?php if ( ! have_posts() ) : ?>
	<div id="post-0" class="post error404 not-found">
		<h1 class="entry-title"><?php _e( 'Not Found', 'templatesquare' ); ?></h1>
		<div class="entry-content">
			<p><?php _e( 'Apologies, but no results were found for the requested archive. Perhaps searching will help find a related post.', 'templatesquare' ); ?></p>
			<?php get_search_form(); ?>
		</div><!-- .entry-content -->
	</div><!-- #post-0 -->
<?php endif; ?>

<?php while ( have_posts() ) : the_post(); ?>

<?php /* How to display all posts. */ ?>
		<div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
			<h2 class="entry-title"><a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Permalink to %s', 'templatesquare' ), the_title_attribute( 'echo=0' ) ); ?>" rel="bookmark"><?php the_title(); ?></a></h2>