Hello,
Did you run the script to see how it works? Checked the script location folder?
If you did, you'd see that it does not need index file, the script generates index page instantly while you visit the site, it is cached for performance, and it's template -index.tpl is in templates folder. If you need modifiaction on any page you do it via templates files.
The install is easy, you follow the instructions and you get a shopping cart site. Many tried and succeeded
If you need any help you are always welcom to this forums.
Kind Regards,
Piotrek