Just create it in a seperate directory called 'testvb'. Did you set up your current forum in a directory called 'forum' or something similar? It would be exactly like that just in the new testvb directory.
Simply did what you did when installing vBulletin, except install it at a different directory. Then password protect that directory, via cPanel. You may have to change the database name in the backup file to have it restore to the new database.
Simply did what you did when installing vBulletin, except install it at a different directory. Then password protect that directory, via cPanel. You may have to change the database name in the backup file to have it restore to the new database.