single-post.php

<?php
/** Template for displaying single posts.
 *
 * @link https://developer.wordpress.org/themes/basics/template-hierarchy/#single-post
 */

// Theme template stuff
// Blah blah

the_loop()

// Load helper functions if we haven't already so that we can call get_reusable_block().
if ( ! function_exists( 'get_reusable_block' ) ) {
	require_once get_stylesheet_directory() . '/inc/helpers.php';
}

//Display 'The Title of My Reusable Block' reusable block.
echo get_reusable_block( 'The Title of My Reusable Block' );