Where to put it? Set the Site’s HTTP URL address

The instruction says clearly:  Set the Site’s HTTP URL address (use the recommended settings. This is a very important setting) in https://milliondollarscript.com/article/cpanel-install/ However, then HOME, the index.html becomes the script page and the entire website is gone. I had to restore it from a backup.  Please someone could explain to me, how can I make it to a separate page at least. Ideal would be as part of a page, like a banner or such. Thank you for your ideas in advance!