You need to ask your host which OS your server has.. but you will need Shell access to the server to install it. You might be better off going with either
http://www.scriptpulse.com or
http://www.slothtrader.com but are also very good scripts that do not require a SLQ database or a shell account to install.
AT3 is a good script, but I'm guess if you don't know your OS, you likely will not have shell access.