This appears to be a website that you use in order to learn about different kinds of locks in PostgreSQL. There is nothing to install AFAICT. You browse this site with your web browser.
site says: "this tool shows ...", so I assumed there is a tool I need to install.
It looks like the site itself is a tool, to figure out what kind of lock you want to use / debug.
That's weird to refer to a site as a tool. A 'service' - that I'd understand, but a tool? It looks like there is actually all this information is also available as a (probably CLI?) tool.