ok, so most of the commands there are terminal/CLI commands.
For the most part you copy+paste in the commands and run them in the terminal. The normal Raspberry Pi OS will be an "Ubuntu" version, not "Arch". (there is a different command labelled for each)
It says to "clone" the repository, thats basically just another word for downloading it.
Click the green button near the top of the page, and then select "download as zip"
After it downloads you'll need to extract the zip file to a folder then navigate to that folder in the terminal.
The command "CD" lets you do that (Change Directory)
eg, CD /home/Hannah
Will take you to the home drive of the user Hannah (not sure what name you set it up with)
Then you can run the other scripts there.
Give it a go.
Be warned, things will probably go wrong and it's best if you try and do a bit of research yourself. It might seem like giberish at the start, but you'll slowly start picking up on things and connecting the dots as to how some things work and what the commands actually mean.
This will give you a decent overview of some of the commands and the way some things work
https://raspberrypi-guide.github.io/programming/working-with-the-command-line
don't be afraid to break it. The worst you can do is need to wipe the SD Card and re-load the software like you've already done.