hi,
turn on debug mode on a testboard (remember you are requirerd to htaccess this and call it testvb).open includes/config.php and righter after the "<?php"
PHP Code:
$config['Misc']['debug'] = 1;
adding a custom field into a existing vBulletin table is done through MySQL.You need to put code for the SQL query in your product install code.You also need to put code to delete the added field in your product uninstall code and so on ...