it's part of it already
once you play the game and it goes to submit a score it's at the bottom..
if you would like it on the main page. they will be able to rate the game with out playing it, you will need to un-comment it..
you can find it
in your root arcade.php
search for
Code:
//no rating here, play game to rate!
//$rating .= $this->html->rate_link($the_game['gid']);
and uncomment so it looks like this
Code:
//no rating here, play game to rate!
$rating .= $this->html->rate_link($the_game['gid']);