Help me get my VB to look like my old PHPBB

[FreeFall0]

I am in the process of converting from PHPBB to VB and i am having some problems in displaying my advert banners exactly where i want them.
I think i know which files to edit, but when i do the page doesnt look like i want it to (i am rubbish at HTML).

I want a banner on the top right of the forum page, the same for the posting page and the same for the header. The templates i have been trying to edit are:
showthread
Header
Forum Display

The code i am tring to put in is:

  <table width="100%" cellspacing="2" cellpadding="2" border="0" align="center">
    <tr> 
      <td colspan="2" align="left" valign="bottom" width="100%"><table align="RIGHT" width="468" border="0" height="68">
          <tr> 
            <td><script language='JavaScript' src='http://www.lushforums.com/phpAdsNew/adjs.php?clientID=18&target=_blank&withText=0'></script></td>
          </tr>
        </table> 

Please could someone tell me exactly where to insert this code. I Have Attached a pic to show where abouts i want it (It is from my PHPBB not my VB)

--edit--
I have got in in the header now, but i havent got it in the forum or showthread pages yet.

[FreeFall0]

When i put the code under the $navbar the code goes behind the table (see screenshot)