make directory
mkdir -p /var/www/phpbb
download phpbb
wget -P /var/www/ https://download.phpbb.com/pub/release/3.3/3.3.12/phpBB-3.3.12.tar.bz2
decompress the file, delete the file and rename the directory
cd /var/www
tar xjvf phpBB-3.3.12.tar.bz2
rm phpBB-3.3.12.tar.bz2
mv phpBB3/ phpbb
make config.php and store/ cache/ files/ images/avatars/upload/ writable
chmod 666 config.php
chmod -R 777 store/ cache/ files/ images/avatars/upload/
INSTALL USING THE INSTALLER VIA WEB
change config.php permissions back to something safe
chmod 644 config.php
remove the install directory
rm -rf install/
if loging out and login back fails clear cookies and cache or try other browser