If you prefer the forum in the same frame as the main frame of the admin cp, it could hardly be easier to accomplish, pure html..
[2.2.6] In
admin/index.php find...
PHP Code:
<td align="right"><b><a href="../index.php?s=<?php echo $session[sessionhash]; ?>" target="_blank">Go to your Forums Home Page</b></b></TD>
change to
PHP Code:
<td align="right"><b><a href="../index.php?s=<?php echo $session[sessionhash]; ?>" target="main">Go to your Forums Home Page</b></b></TD>
Finally reload the top frame of your admin cp, the thin one that holds a link labeled "Go to your Forums Home Page", it now points to the frame beneath.