In order to run this site locally, whether it's to play around with it or to help contribute, you first need to download the website's files.
You can either use git pull to download, or download a .zip file from the GitHub page by clicking the green Code button then Download ZIP, and then unzip somewhere.
After downloading the source files, install Zola following instructions on their website.
If you're just running locally in a "development" environment, just use your computer's terminal application (i.e. Windows PowerShell, MacOS Terminal, gnome-terminal, etc.) to cd into the folder downloaded earlier, then run zola serve
If you want to build the site and host it elsewhere, it's better to learn how on Zola's website.