Paste this code in wp-content\plugins\tinymce-advanced\tinymce-advanced.php

add_filter('mce_css', 'tuts_mcekit_editor_style');
function tuts_mcekit_editor_style($url) {

if ( !empty($url) )
$url .= ‘,’;

// Retrieves the plugin directory URL and adds editor stylesheet
// Change the path here if using different directories
$url .= trailingslashit( plugin_dir_url(__FILE__) ) . ‘/editor-css.css’;

return $url;

editer-css.css is css file name and paste it in plugin’s directory wp-content\plugins\tinymce-advanced\

and  in TinyMCE Advanced settings page, and dropped the new “Styles” drop-down box on the editor toolbar and save changes.