在苏尼尔的回答的帮助下，我确切地知道了我需要做什么。

我去下载了免费版本的Metaboxhttps://wordpress.org/plugins/meta-box/

一旦我下载了它，我就把它放在child-theme/external/meta-box并引用自child-theme/inc/events-custom-post-type.php.

events-custom-post-type.php 看起来像这样。

require_once(get_stylesheet_directory() . \'/external/meta-box/meta-box.php\');

function custom_events ()
{
    $labels = array(
        \'name\' => \'Events\',
        \'singular_name\' => \'Event\',
        \'add_new\' => \'Add Event\',
        \'all_items\' => \'All Events\',
        \'add_new_item\' => \'Add Event\',
        \'edit_item\' => \'Edit Event\',
        \'new_item\' => \'New Event\',
        \'view_item\' => \'View Event\',
        \'search_item_label\' => \'Search Events\',
        \'not_found\' => \'No Events Found\',
        \'not_found_in_trash\' => \'No Events Found in Trash\',
        \'parent_item_colon\' => \'Parent Event\'
    );

    $args = array(
        \'labels\' => $labels,
        \'public\' => true,
        \'has_archive\' => true,
        \'publicly_queryable\' => false,
        \'query_var\' => true,
        \'rewrite\' => true,
        \'capability_type\' => \'post\',
        \'hierarchical\' => true,
        \'supports\' => array(
            \'title\',
            \'editor\',
        ),
        \'menu_icon\' => \'dashicons-calendar-alt\',
        \'menu_position\' => 5,
        \'exclude_from_search\' => true
    );

    register_post_type( \'custom_events_post_type\', $args );
}

function prefix_register_meta_boxes_events( $meta_boxes ) {
    $prefix = \'custom_event_\';

    $meta_boxes[] = array(
        \'id\'         => $prefix . \'details\',
        \'title\'      => \'Event details\',
        \'post_types\' => \'custom_events_post_type\',
        \'context\'    => \'normal\',
        \'priority\'   => \'high\',

        \'fields\' => array(
            array(
                \'name\'  => \'Event date\',
                \'desc\'  => \'Select event date\',
                \'id\'    => $prefix . \'date\',
                \'type\'  => \'date\',
            ),
            array (
                \'name\' => \'Event location\',
                \'desc\' => \'Location of the event\',
                \'id\'   => $prefix . \'location\',
                \'type\' => \'text\'
            )
        )
    );

    return $meta_boxes;
}

add_action( \'init\', \'custom_events\' );

add_filter( \'rwmb_meta_boxes\', \'prefix_register_meta_boxes_events\' );

你只需要确保prefix_register_meta_boxes_events 函数，其中显示post_types 添加您自己的自定义帖子类型注册为的内容。

之后，我在中引用了此文件child-theme/functions.php 就像这样。

require get_stylesheet_directory() . \'/inc/events-custom-post-type.php\';