Well, a quick google search came up with http://www.download-ftp-center.com/mirrors.html
To install it, go to the directory you saved the file to and make sure the file is executable. To do that just type chmod +x filename. Then type ./filename The "./" tells it to look in the current directory for the file. That's it. Assuming your system is correctly setup you should just be able to type et to start the game. I think it's et, it's been awhile since I played. Good Luck!