Well all you should have to do is upgrade your forum and follow the upgrade instructions for vb5 in our documentation.
IMPORTANT - FOR VBULLETIN 5 ONLY.
1. You can do either one of the options above after uploading all the files noted above in the normal upgrade procedure.
Edit your config-int.php file on your server and add the line below right above the define for VB3_INTEGRATION
Edit the new config-int.php file in the downloaded code with all the proper server paths urls etc and upload it to your server.
2. Copy the pp.php file from the install directory into your vBulletin forums root directory ( This is the root directory not any subdirectories ).
3. Make a copy your vb config.php file from vbulletin install and place that copy into your photopost directory.
You must edit this config.php file you put in your photopost directory as it uses this to get the forum path.
$config['core_path'] = realpath(dirname(__FILE__)) . '/core';
You need to change it to something like this which has the actual correct path to your forums core directory.
$config['core_path'] = '/var/www/yoursite/path/to/vbulletin/core';
Save your changes!