How to use or add?

Paste the code to your theme’s root file functions.php or you can use it in your custom plugin’s starter file with the add_filter hook.

<?php
add_filter( 'tp_meta_boxes', 'themepure_metabox' );
function themepure_metabox( $meta_boxes ) {
    $meta_boxes[] = array(
        'metabox_id'       => '_your_id',
        'title'    => esc_html__( 'Your Metabox Title', 'textdomain' ),
        'post_type'=> 'post', // page, custom post type name
        'context'  => 'normal',
        'priority' => 'core',
        'fields'   => array(),
    );

    return $meta_boxes;
}

?>

Note: You must return multidimensional array otherwise you will get ERROR!