post-featured-image (width="100%" height="100%")

The first question I have decided! ??

figure img {
width: 100%;
}

The second question, I do not know how to solve. Tell me what to do so that thumbnail images are displayed when viewing the post?

The answer to the second question <?php the_post_thumbnail(‘full’); ?>

/wp-content/themes/accelerate/content-single.php:

<?php
/**
 * The template used for displaying page content in page.php
 *
 * @package ThemeGrill
 * @subpackage Accelerate
 * @since Accelerate 1.0
 */
?>

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
	<?php do_action( 'accelerate_before_post_content' ); ?>

	<div id="post-header-image-v1" style="margin-bottom: -62px;">
	<?php the_post_thumbnail('full'); ?>
	</div>

	<div id="post-header-text-v1" style="background: rgba(255, 255, 255, 1); padding: 14px 0px 0px 0px; box-shadow: 0px -3px 0px 0px rgba(119, 204, 109, 0.78); position: relative;">
	<header class="entry-header">
		<h1 class="entry-title">
			<?php the_title(); ?>
		</h1>
	</header>

	<?php accelerate_entry_meta(); ?>
	</div>

	<div class="entry-content clearfix">
		<?php
			the_content();

			wp_link_pages( array(
				'before'            => '<div style="clear: both;"></div><div class="pagination clearfix">'.__( 'Pages:', 'accelerate' ),
				'after'             => '</div>',
				'link_before'       => '<span>',
				'link_after'        => '</span>'
	      ) );
		?>
	</div>

	<?php do_action( 'accelerate_after_post_content' ); ?>
</article>

There styles are spelled wrong.
Here is the code without the styles:
/wp-content/themes/accelerate/content-single.php

<?php
/**
 * The template used for displaying page content in page.php
 *
 * @package ThemeGrill
 * @subpackage Accelerate
 * @since Accelerate 1.0
 */
?>

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
	<?php do_action( 'accelerate_before_post_content' ); ?>

	<div id="post-header-image-v1" style="">
	<?php the_post_thumbnail('full'); ?>
	</div>

	<div id="post-header-text-v1" style="">
	<header class="entry-header">
		<h1 class="entry-title">
			<?php the_title(); ?>
		</h1>
	</header>

	<?php accelerate_entry_meta(); ?>
	</div>

	<div class="entry-content clearfix">
		<?php
			the_content();

			wp_link_pages( array(
				'before'            => '<div style="clear: both;"></div><div class="pagination clearfix">'.__( 'Pages:', 'accelerate' ),
				'after'             => '</div>',
				'link_before'       => '<span>',
				'link_after'        => '</span>'
	      ) );
		?>
	</div>

	<?php do_action( 'accelerate_after_post_content' ); ?>
</article>

/wp-content/themes/accelerate/content-single.php

Please add the possibility to enable or disable the thumbnail in the posts.
Because when you update the theme code flies. And you need to register it again

<?php
/**
 * The template used for displaying page content in page.php
 *
 * @package ThemeGrill
 * @subpackage Accelerate
 * @since Accelerate 1.0
 */
?>

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
	<?php do_action( 'accelerate_before_post_content' ); ?>

	<div id="post-header-image-v1" style="">
	<?php the_post_thumbnail('full'); ?>
	</div>

	<div id="post-header-text-v1" style="">
	<header class="entry-header">
		<h1 class="entry-title">
			<?php the_title(); ?>
		</h1>
	</header>

	<?php accelerate_entry_meta(); ?>
	</div>

I added the new code. To a social message is displayed picture.

/wp-content/themes/accelerate/content-single.php

<?php
/**
 * The template used for displaying page content in page.php
 *
 * @package ThemeGrill
 * @subpackage Accelerate
 * @since Accelerate 1.0
 */
?>

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
	<?php do_action( 'accelerate_before_post_content' ); ?>

	<meta property="og:image" content='<?php the_post_thumbnail('full'); ?>'/>
	<meta itemprop="image" content='<?php the_post_thumbnail('full'); ?>'/>
	<meta name="twitter:image:src" content='<?php the_post_thumbnail('full'); ?>'/>
	<link rel="image_src" href='<?php the_post_thumbnail('full'); ?>'/>

	<div id="post-header-image-v1" style="">
	<?php the_post_thumbnail('full'); ?>
	</div>

	<div id="post-header-text-v1" style="">
	<header class="entry-header">
		<h1 class="entry-title">
			<?php the_title(); ?>
		</h1>
	</header>

	<?php accelerate_entry_meta(); ?>

	<div class="entry-content clearfix">
		<?php
			the_content();

			wp_link_pages( array(
				'before'            => '<div style="clear: both;"></div><div class="pagination clearfix">'.__( 'Pages:', 'accelerate' ),
				'after'             => '</div>',
				'link_before'       => '<span>',
				'link_after'        => '</span>'
	      ) );
		?>
	</div>

	<?php do_action( 'accelerate_after_post_content' ); ?>
</article>

Accelerate 1.0.9 (Last Updated: 2014-11-05):

Tell me how to make that image was the whole width 100% and height 100%;?

This code used to work, but now stopped:

figure img {
width: 100%;
}

Now when loading images in thumbnail substituted link (-720×300.jpg)

<figure class="post-featured-image">
<a href="https://mysite.com/kakoj-noutbuk-kupit-dlya-raboty/" title="Какой ноутбук купить для работы">

<img width="720" height="300" src="https://mysite.com/wp-content/uploads/Kakoy-noutbuk-kupit-dlya-raboty-720x300.jpg" class="attachment-featured-blog-large wp-post-image" alt="Какой ноутбук купить для работы" title="Какой ноутбук купить для работы">

</a>
</figure>

I found!

1. We need to open the file: functions.php

2. Change this code:
add_image_size( 'featured-blog-large', 720, 300, true );
on this code:
add_image_size( 'featured-blog-large', 720, 500, true );

3. Delete the downloaded image of WordPress. Delete the admin panel.

4. Upload image again. And it will be clipped with a new size 720×500.jpg

Hey Vadim V.
You save my life with the code to display featured image when viewing the post (without the styles).
Thank you so much for your help!

Welcome! ??

Hello…do you know how can i put my homepage exactly as the one showed on Themegrill Accelerate “Live Demo” website?

I mean…with that 3 images underneath the slider?

Thanks in advance

https://themegrill.com/theme-instruction/accelerate/#businesstemplate