A complete setup with many options can be performed by running the script at git.io/squishbox with the command
curl -L git.io/squishbox | bash
To perform the minimal steps to set up, first install the required software: Connect to your Pi via ssh or plug in a keyboard and monitor and type in the following commands to install the required software:
sudo apt install git python3-pip libfluidsynth1 fluid-soundfont-gm
sudo pip3 install oyaml RPLCD RPi.GPIO