Need help adding three dots […] to my post excerpts?

What theme are you using? Unless you’re using the exact same theme as the person from the thread you linked, the code provided in that thread won’t be of much use to you. What is the exact code you were using?

Oh…ok.

I’m using the theme:
MH Newsdesk lite

Here is the function.php code
MH Newsdesk lite: Theme Functions (functions.php)

<?php

/***** Fetch Options *****/

$mh_newsdesk_lite_lite_options = get_option('mh_newsdesk_lite_options');

/***** Custom Hooks *****/

function mh_newsdesk_lite_before_page_content() {
    do_action('mh_newsdesk_lite_before_page_content');
}

function mh_newsdesk_lite_before_post_content() {
    do_action('mh_newsdesk_lite_before_post_content');
}

/***** Theme Setup *****/

if (!function_exists('mh_newsdesk_lite_themes_setup')) {
	function mh_newsdesk_lite_themes_setup() {
		$header = array(
			'default-image'	=> '',
			'default-text-color' => '1f1e1e',
			'width' => 300,
			'height' => 100,
			'flex-width' => true,
			'flex-height' => true
		);
		add_theme_support('custom-header', $header);

		load_theme_textdomain('mh-newsdesk-lite', get_template_directory() . '/languages');

		add_post_type_support('page', 'excerpt');

		add_theme_support('automatic-feed-links');
		add_theme_support('html5', array( 'search-form'));
		add_theme_support('custom-background', array('default-color' => 'efefef'));
		add_theme_support('post-thumbnails');

		add_image_size('content-single', 777, 437, true);
		add_image_size('content-list', 260, 146, true);
		add_image_size('cp-thumb-small', 120, 67, true);

		register_nav_menus(array(
			'main_nav' => __('Main Navigation', 'mh-newsdesk-lite'),
		));

		add_filter('use_default_gallery_style', '__return_false');
		add_filter('widget_text', 'do_shortcode');
	}
}
add_action('after_setup_theme', 'mh_newsdesk_lite_themes_setup');

/***** Set Content Width *****/

if (!function_exists('mh_newsdesk_lite_content_width')) {
	function mh_newsdesk_lite_content_width() {
		global $content_width;
		if (!isset($content_width)) {
			if (is_page_template('page-full.php')) {
				$content_width = 1180;
			} else {
				$content_width = 777;
			}
		}
	}
}
add_action('template_redirect', 'mh_newsdesk_lite_content_width');

/***** Load CSS & JavaScript *****/

if (!function_exists('mh_newsdesk_lite_scripts')) {
	function mh_newsdesk_lite_scripts() {
		wp_enqueue_style('mh-google-fonts', "https://fonts.googleapis.com/css?family=Oswald:400,700,300|PT+Serif:400,400italic,700,700italic", array(), null);
		wp_enqueue_style('mh-font-awesome', get_template_directory_uri() . '/includes/font-awesome.min.css', array(), null);
		wp_enqueue_style('mh-style', get_stylesheet_uri(), false, '1.1.0');
		wp_enqueue_script('mh-scripts', get_template_directory_uri() . '/js/scripts.js', array('jquery'));
		if (!is_admin()) {
			if (is_singular() && comments_open() && (get_option('thread_comments') == 1))
				wp_enqueue_script('comment-reply');
		}
	}
}
add_action('wp_enqueue_scripts', 'mh_newsdesk_lite_scripts');

if (!function_exists('mh_newsdesk_lite_admin_scripts')) {
	function mh_newsdesk_lite_admin_scripts($hook) {
		if ('appearance_page_newsdesk' === $hook || 'widgets.php' === $hook) {
			wp_enqueue_style('mh-admin', get_template_directory_uri() . '/admin/admin.css');
		}
	}
}
add_action('admin_enqueue_scripts', 'mh_newsdesk_lite_admin_scripts');

/***** Register Widget Areas / Sidebars	*****/

if (!function_exists('mh_newsdesk_lite_widgets_init')) {
	function mh_newsdesk_lite_widgets_init() {
		register_sidebar(array('name' => __('Global Sidebar', 'mh-newsdesk-lite'), 'id' => 'sidebar', 'description' => __('Sidebar used globally throughout your site.', 'mh-newsdesk-lite'), 'before_widget' => '<div class="sb-widget clearfix">', 'after_widget' => '</div>', 'before_title' => '<h4 class="widget-title"><span>', 'after_title' => '</span></h4>'));
		register_sidebar(array('name' => __('Home 1 - Large Column (Top)', 'mh-newsdesk-lite'), 'id' => 'home-1', 'description' => __('Large column on Homepage.', 'mh-newsdesk-lite'), 'before_widget' => '<div class="sb-widget">', 'after_widget' => '</div>', 'before_title' => '<h4 class="widget-title"><span>', 'after_title' => '</span></h4>'));
		register_sidebar(array('name' => __('Home 2 - First Column', 'mh-newsdesk-lite'), 'id' => 'home-2', 'description' => __('First column on Homepage.', 'mh-newsdesk-lite'), 'before_widget' => '<div class="sb-widget">', 'after_widget' => '</div>', 'before_title' => '<h4 class="widget-title"><span>', 'after_title' => '</span></h4>'));
		register_sidebar(array('name' => __('Home 3 - Second Column', 'mh-newsdesk-lite'), 'id' => 'home-3', 'description' => __('Second column on Homepage.', 'mh-newsdesk-lite'), 'before_widget' => '<div class="sb-widget">', 'after_widget' => '</div>', 'before_title' => '<h4 class="widget-title"><span>', 'after_title' => '</span></h4>'));
		register_sidebar(array('name' => __('Home 4 - Large Column (Bottom)', 'mh-newsdesk-lite'), 'id' => 'home-4', 'description' => __('Large column on Homepage.', 'mh-newsdesk-lite'), 'before_widget' => '<div class="sb-widget">', 'after_widget' => '</div>', 'before_title' => '<h4 class="widget-title"><span>', 'after_title' => '</span></h4>'));
		register_sidebar(array('name' => __('Home 5 - Sidebar', 'mh-newsdesk-lite'), 'id' => 'home-5', 'description' => __('Sidebar on Homepage.', 'mh-newsdesk-lite'), 'before_widget' => '<div class="sb-widget">', 'after_widget' => '</div>', 'before_title' => '<h4 class="widget-title"><span>', 'after_title' => '</span></h4>'));
	}
}
add_action('widgets_init', 'mh_newsdesk_lite_widgets_init');

/***** Include Several Functions *****/

require_once('includes/mh-options.php');
require_once('includes/mh-custom-functions.php');
require_once('includes/mh-widgets.php');

if (is_admin()) {
	require_once('admin/admin.php');
}

?>

How are you adding the posts to your sidebar? Are you using a plugin to generate these badges? I installed the MH Newsdesk theme and I see ... at the end of all of my excerpts.

using Badgeos
widget to the sidebar

Which widget are you using? Are you using one of the built-in WordPress widgets or are you using one of the custom widgets supplied by either the BadgeOS plugin or the MH Newsdesk theme? Can you post a link to your site?