For Minecraft Java

Download the zip file here.

Copy the folder inside into your Minecraft save folder.

To find this, the Mojang website explains:

Minecraft on Windows
Press Win+R, then type %appdata%\.minecraft, then press Ok.

In the Finder, from the Go menu, select ‘Go to Folder’, then type: ~/Library/Application Support/minecraft, and click Go.

The next time you load up Minecraft, Saint Lauretia should be an option in the saved worlds.