Category page with a sort function by custom field

Hi Mark,

You can use the function query_posts() or create a new instance WP_Query in the archive template file of the theme with the arguments orderby and meta_key to sort the post in the archive page by the field number value.

query_posts(
    array(  
        'order'     => 'DESC',
        'meta_key' => 'field_id',
        'orderby'   => 'meta_value_num', //or 'meta_value_num'                
    )
);

$args = array(
    'post_type' => 'post',
    'orderby'   => 'meta_value_num',
    'meta_key'  => 'field_id',
);
$query = new WP_Query( $args );

and display the field value of each post by using the helper function rwmb_meta in the template parts file.

For more information, please follow the documentation.
https://developer.wordpress.org/reference/classes/wp_query/#order-orderby-parameters
https://developer.wordpress.org/reference/functions/query_posts/
https://wordpress.stackexchange.com/questions/15477/custom-query-with-orderby-meta-value-of-custom-field