You need to use a shell to start with FortressJS. A shell is a window/program in which you enter commands. This commands are interpreted and do actions on the operating system.
To Start with FortressJS, we need to use NodeJS. NodeJS will "execute" our FortressJS app.
We need to install NodeJS to use it. This tutorial uses a Debian system, so you can enter this command to install it :
apt-get install -y nodejs
You got it ? Well done ! Go to the next chapter