将此代码放在当前活动主题中function.php 文件

function wpdocs_theme_name_scripts() {
    wp_enqueue_style(\'my-styles\',get_template_directory_uri() . \'/mystyles.css\',array(\'plugin-style-handle\'));
    }
add_action( \'wp_enqueue_scripts\', \'wpdocs_theme_name_scripts\' );