All the sub-folders contain two files:
• index.html
• sketch.js
There's no need to change the index.html files. They're ready to use.
The sketch.js files are all empty and ready ro receive the p5js code.
These files should be edited in a plain text editor such as Notepad.
You can navigate to the page you want in the web browser.
Or open any index.html file diectly in the Web Browser.
This will display the result of the sketch.js code.