quero criar esse código para as páginas

add_action( 'add_meta_boxes', 'meta_box_video' );
function meta_box_video()
{
    add_meta_box( 'video-meta-box-id', 'Video Embed', 'meta_box_callback', 'post', 'normal', 'high' );
}

function meta_box_callback( $post )
{
    $values = get_post_custom( $post->ID );
    $selected = isset( $values['meta_box_video_embed'] ) ? $values['meta_box_video_embed'][0] : '';

    wp_nonce_field( 'my_meta_box_nonce', 'meta_box_nonce' );
    ?>
    <p>
        <label for="meta_box_video_embed"><p>Video Embed</p></label>
        <textarea name="meta_box_video_embed" id="meta_box_video_embed" cols="62" rows="5" ><?php echo $selected; ?></textarea>
    </p>
    <p>Leave it Empty ( if you want to use an image thumbnail ) .</p>
    <?php   
}

add_action( 'save_post', 'meta_box_video_save' );
function meta_box_video_save( $post_id )
{
    // Bail if we're doing an auto save
    if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) return;

    // if our nonce isn't there, or we can't verify it, bail
    if( !isset( $_POST['meta_box_nonce'] ) || !wp_verify_nonce( $_POST['meta_box_nonce'], 'my_meta_box_nonce' ) ) return;

    // if our current user can't edit this post, bail
    if( !current_user_can( 'edit_post' ) ) return;

    // now we can actually save the data
    $allowed = array( 
        'a' => array( // on allow a tags
            'href' => array() // and those anchords can only have href attribute
        )
    );

    // Probably a good idea to make sure your data is set

    if( isset( $_POST['meta_box_video_embed'] ) )
        update_post_meta( $post_id, 'meta_box_video_embed', $_POST['meta_box_video_embed'] );

}