vBulletin is one of the finest and most popular message board software packages available on the Internet . The installation process is rather involved, but not as complicated as you may think.
The two main requirements are that you have PHP and MySQL installed on your server. If that is the case, then you can move forward with the installation process.
After you purchase a license, you will be sent a customer number and password. You will use this to log in to http://members.vbulletin.com, and that is where you will download the vBulletin software.

Before uploading the software, ensure that you have created a MySQL database. This can be done easily from your Cpanel control panel.
Extract the software, and then log in to your hosting account with your favorite FTP application. You will be uploading the contents of the “upload” folder into the folder that you want the forums in. In other words, if you want to install into the “forums” folder on your site, create that folder, and go into that directory.
Then, go into the “upload” directory on your computer, and edit the config.php file with your favorite text editor. Fill in the database name, username, and password where indicated. Save the file, and then start uploading the contents of the entire “upload” folder, including all folders within.
Now, you will begin the installation process. Navigate to the install/install.php folder. Example:

http://www.domain.com/forums/install/install.php

You will be prompted for your customer number and password, and after verification, the installation process will begin. After verifying your config.php file, and your database, you will be prompted through a series of steps that will populate your database tables, and set up the software.
Fill in the information pertaining to your site and administrator account when prompted, and when finished, and prompted to do so, make sure to delete or rename the install.php file, for security reasons.