I have a Raspberry Pi 3 with a 32 GB SD card that I put a pre-made image with emulation station on. It launches emulation station on boot and I installed the desktop so that I can use the Pi like a normal one running Raspbian when I want to. My problem is that I don't have all of the programs that come default with a Rapsbian image. I really like the way I have emulation station set up so I want to know how to install the programs without having to redo all the customisation and games on the Pi.
To install any software, simply run the command:
sudo apt-get update (this updates the list of repositories and which version of which software is available)
followed by the command
sudo apt-get install name_of_software_package
In the case of Sonic Pi, the package name is