This is the tutorial that i have found for you.
Go to
http://www.phpbb.com and download the phpbb2 files.
Download FileZilla and log into it using your username and password.
If its a rar archive, unzip it and then upload that will be usefull for you, but i can eat up your bandwidth.
Upload all of the files you just downloaded into public_html( Web Root) directory.
The find config.php.
Right click and select File Attributes
Make the numbers at the bottom of the page 666
The go into your brower and in the url box type:
http://yoursite.x10hosting.com/install/install.php
Select MySQL 4.x/5.x from the drop down.
Leave 'localhost' as it is.
enter your database name
user name and password for that database
Then follow the easy instructions for the rest.
Click start install, and then finish installtion.
After that go back to FileZilla and delete the 'install' folder, and the 'contrib' file.
Then go back to your browser and refresh the page, log in the then log into the Admin Control panel.