Make thumbnails clickable link to posts

Ok, found where to put code, “tern_wp_youtube_image();” ,in post.php to make thumbnails show on http://www.autoclips.com/category/car-dealers/ but have no idea on how to make these thumbnails clickable links to posts. Not a php expert or even a wordpress expert for that matter so any help you can give would be greatly appreciated. Thanks

http://ww.wp.xz.cn/extend/plugins/automatic-youtube-video-posts/