$ sudo apt-get update
$ sudo apt-get install rhythmbox-plugin-magnatune 

rhythmbox-plugin-magnatune is installed in your system.

Make ensure the rhythmbox-plugin-magnatune package were installed using the commands given below,

$ sudo dpkg-query -l | grep rhythmbox-plugin-magnatune *

You will get with rhythmbox-plugin-magnatune package name, version, architecture and description in a table

rhythmbox-plugin-magnatune package basic information: