in order to opt into beta you need node.js and git.
now that that's installed you can clone the project on your desktop by typing in the command prompt:
git clone https://github.com/77z/os.git
now you should have a folder called os somewhere.
next just change the directory of the command prompt to the "os" folder.
cd os
now type
npm start
and you're up and running!
if a new version comes out go into the terminal on the OS folder and type
git pull
also with latest version there is auto updating!!