Hi Michelle,
I changed
<div class="site-branding">
<?php
if ( is_front_page() && is_home() ) : ?>
<h1 class="site-title"><a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home"><?php bloginfo( 'name' ); ?></a></h1>
<?php else : ?>
<p class="site-title"><a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home"><?php bloginfo( 'name' ); ?></a></p>
<?php endif;
$description = get_bloginfo( 'description', 'display' );
if ( $description || is_customize_preview() ) : ?>
<p class="site-description"><?php echo $description; ?></p>
<?php endif;
?>
<button class="secondary-toggle"><?php _e( 'Menu and widgets', 'twentyfifteen' ); ?></button>
</div><!-- .site-branding -->
from the original Twenty Fifteen theme in header.php to
<div class="site-branding">
<?php
if ( is_front_page() && is_home() ) : ?>
<h1 class="site-title"><a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home"><?php bloginfo( 'name' ); ?><img src="image.png" height="151" width="248"></a></h1>
<?php else : ?>
<p class="site-title"><a href="<?php echo esc_url( home_url( '/' ) ); ?>" rel="home"><?php bloginfo( 'name' ); ?><img src="image.png" height="151" width="248"></a></p>
<?php endif;
$description = get_bloginfo( 'description', 'display' );
if ( $description || is_customize_preview() ) : ?>
<p class="site-description"><?php echo $description; ?></p>
<?php endif;
?>
<button class="secondary-toggle"><?php _e( 'Menu and widgets', 'twentyfifteen' ); ?></button>
</div><!-- .site-branding -->
</header><!-- .site-header -->
(where “image.png” is the location of my site’s logo) in my child theme. I decided to take out the words in the site title because they weren’t needed.
Hope that helps!