The best open source forum software available is phpBB3. I have been using phpbb for years. The best paid for forum is vBulletin. Both phpBB and vBulletin have their advantages and disadvantages, however, since phpBB is free, its the best option in my opinion. The following video guides you through the phpBB installation process. The video assumes that you have set up your database and have uploaded all of the phpBB files onto your server and are ready to install.