that depends on where you want to display the ad
if its after specific posts, you can add a plug in on hook postbit display complete (code provided to me from MarkFL)
PHP Code:
global $ids;
$excluded = 88; //if you have a Usergroup to exclude from seeing Ads
if (!is_member_of($vbulletin->userinfo, $excluded) AND $post['postid'] == $ids[2] AND THIS_SCRIPT !== 'private')
{
$template_hook['postbit_end'] .= '
<CENTER>
AD CODE
</CENTER> ';
}
if you wanted to go below the navbar, you can use the Ad Location Template --> ad_navbar_below
I also on my site have ads on my Forumhome, UserCP.... depends on where you want to go with it.