If the original post’s code is all the code you have, then nothing should happen. If you are unfamiliar with getting the setup for p5js, then I suggest you use their in-browser editor environment: https://editor.p5js.org/
Otherwise, I highly recommend the earlier videos by The Coding Train (Dan Shiffman), where he explains the fundamentals of using p5js locally.
The typical workflow is (and you can find this in the p5js docs):
Create an HTML file that uses a script tag to link to the p5js CDN
Add another script tag linking your local JavaScript file
Then, the p5js library (i.e. functions) are available for use within the linked local JS file
Not sure, if this will be helpful enough, as everybody’s situation is different, but I have set up VS Code and Node JS. This way, I work on *.js files in Code, and cd into the dir with that file, and run it with Node using node filename.js
It’s a little bit different than the editor here (e.g., return normally shows nothing when *.js files are run, so I debug while coding by using console.log("debug text here")
I’m also finding Node to be extremely useful, even on its own (e.g., I type anything I want to check, and it shows the result immediately). The same can be done with a browser console, though.
I easily switch between Code and Node by Ctrl + ` (Control + backtick char). I haven’t tried to play sound or video files with it yet, though