[osayidan]

find in 'FORUMHOME' template:

<table cellpadding="0" cellspacing="2" border="0" width="100%">
<tr valign="bottom">
	<td>
		<table cellpadding="2" cellspacing="0" border="0">
		<tr>
			<td><img src="$stylevar[imgdir_statusicon]/forum_new.gif" alt="$vbphrase[contains_new_posts]" border="0" /></td>
			<td class="smallfont">&nbsp; $vbphrase[forum_contains_new_posts]</td>
		</tr>
		<tr>
			<td><img src="$stylevar[imgdir_statusicon]/forum_old.gif" alt="$vbphrase[contains_no_new_posts]" border="0" /></td>
			<td class="smallfont">&nbsp; $vbphrase[forum_contains_no_new_posts]</td>
		</tr>
		<tr>
			<td><img src="$stylevar[imgdir_statusicon]/forum_old_lock.gif" alt="$vbphrase[a_closed_forum]" border="0" /></td>
			<td class="smallfont">&nbsp; $vbphrase[forum_is_closed_for_posting]</td>
		</tr>
		</table>
</td>

add bellow:

<td>
<!--- ad code here --->
</td>

this should work, may want to add padding or other css elements to make it look nicer.