1. Install GalliumOS - search Google for this there are lots of guides for how to do this for chromebooks
2. Install Itch
3. Install thiss game
The game itself is in Python using RenPy, so you can run it on almost any OS apart from ChromeOS because it's a locked down version of Linux. It has launchers for windows and linux grouped under the windows download, so if you install GalliumOS or another Linux that works on chromebooks then install itch it works out-of-the-box!