Use the below simple code to get the image full url.
that url can ve used in many ways like in <img src=""> tag.
in the below i will show you how to use in img tag
$post_image = wp_get_attachment_url(get_post_thumbnail_id($post->ID));
<img src="<?php echo $post_image; ?>" alt="img"/>
Now you can set image width and heignt according to your requirements.