You run a PC. You are using Visual studio Code and you have a powershell terminal opened. From the LHS, it looks as if you have cloned the github repos correctly.
It means that you need to run an http-server. There are many ways to do it and the above instruction are not very prescriptive about how to do it. Since you seem to be familiar with npm, you can install an http-server with the command line (in powershell)
npm install --global http-server
This command need to be issued in a terminal, like the one you have at the bottom of your screenshot.
The next step is to launch the http-server. For this purpose, you need to invoke it from the "root" directory of your project. In your case the root directory is called "the balance".
From the balancing-act directory, you issue in your powershell terminal
cd ..
http-server
At this point, the http-server will start and list some URL. Using a browser, enter the url listed by the http-server. The browser will display the directory structure of the root directory. From the browser, click on balancing-act folder, and then balancing-act_en.html. It should run the simulation at this point.
Best
Martin Veillette