What specifically are you having problems with?
All you need to do to display threads and topics/posts it set it up like so:
Make some functions that take some stuff as arguements, such as the number of threads to show per page or something and the forum id. You can then grab these arguements from the URL via a $_GET['whatever'].
The functions should handle at least showing the threads, maybe more.
<?php
// Stuff here...
// DB connection and such
function ShowThreads($forumID, $numberPerPg)
{
// I assume you have some sort of HTML for this page
// continue it here
?>
<table><td>Thread</td</table>
<?php
for ($i = 0; $i<$row['id']; $i++)
{
echo $row['threadname'];
}
}
?>
Note the above is an example, don't expect to copy>paste it.
Hope this helps!