My b2evolution Version: 2.x

Hello all, I am having trouble adding google ads to my posts. I have carried out the following:

1. > Global Settings > Plugins added and saved this code:

<script type="text/javascript"><!--
google_ad_client = "ca-pub-???????";
/* statuses */
google_ad_slot = "?????";
google_ad_width = 468;
google_ad_height = 60;
//-->
</script>
<script type="text/javascript"
src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>

2. I have then gone to my post/comments and clicked on the Welcome Title and cicked on Edit, I have then clicked on the Adsence tab which insertsbut in preview nothing is showing.... what am I doing wrong? can I not just paste the adsence code into the comment section?