Hi,
Please use this code in the file functions.php in your theme or child theme folder
function new_excerpt_more($more) {
global $post;
return '<a class="moretag" href="'. get_permalink($post->ID) . '"> Read the full article...</a>';
}
add_filter('excerpt_more', 'new_excerpt_more', 99);
For further information, please follow this link
https://codex.wordpress.org/Customizing_the_Read_More
Regards.