Add custom logo

 /**
  * Add logo
  */

function theme_custom_logo_setup() {
    $defaults = array(
        'height'               => 100,
        'width'                => 400,
        'flex-height'          => true,
        'flex-width'           => true,
        'header-text'          => array('site-title', 'site-description'),
        'unlink-homepage-logo' => true,
    );

    add_theme_support('custom-logo', $defaults);
}

add_action('after_setup_theme', 'theme_custom_logo_setup');