Example Custom Meta Boxes use

cmb_example_init.php

<?php
// Initialize the metabox class
function be_initialize_cmb_meta_boxes() {
    if ( !class_exists( 'cmb_Meta_Box' ) ) {
        require_once( 'libs/cmb-library/init.php' );
    }
} add_action( 'init', 'be_initialize_cmb_meta_boxes', 9999 );

cmb_example_use.php

<?php 
// get CMB library here: https://github.com/jaredatch/Custom-Metaboxes-and-Fields-for-WordPress
function kd_example_sidebar_metaboxes( $meta_boxes ) {
    $meta_boxes[] = array(
        'id' => 'sidebar_metabox',
        'title' => 'Sidebar', //this is the metabox, the field container.
        'pages' => array('page','post','event'), // post type
        'context' => 'normal',
        'priority' => 'high',
        'show_names' => false,
        'fields' => array( //this array contains the fields inside the container.
            array(
                'name' => 'Sidebar',
                'id' => 'sidebar',
                'type' => 'wysiwyg',
                'options' => array(
                    'textarea_rows' => 3,
                )
            ),
        )
    );
    return $meta_boxes;
} add_filter( 'cmb_meta_boxes', 'kd_example_sidebar_metaboxes' );