Add READ MORE link to post for Excerpts

I would like to add a READ MORE to the excerpts on the Home Page and Category Pages. How would I do this?

Reading an article elsewhere, I tried the code below in the theme's functions.php file, but it did not work.

// Changing excerpt more
   function new_excerpt_more($more) {
   global $post;
   return '… <a href="'. get_permalink($post->ID) . '">' . 'Read More »' . '</a>';
   add_filter('excerpt_more', 'new_excerpt_more');