First, you need a web server to properly display HTML files. While Google Drive allows public sharing, it is not a web server and will not display the pages directly to browsers.
So step one is that you need to get an actual web host. There are some sites that offer free/cheap hosting (like neocities mentioned in the wix post), or you can go with more dedicated approaches and your own domain name (here at Tumult we use WebFaction but there are plenty of great options).
After you have a web host, you’ll use a program (typically SFTP-based) to upload your files to that host. You’ll then be able to view them on the web via a URL.
Finally, this URL can be entered with the <iframe> code as in the wix post.