$ sudo apt-get update
$ sudo apt-get install mypaint-data-extras 

mypaint-data-extras is installed in your system.

Make ensure the mypaint-data-extras package were installed using the commands given below,

$ sudo dpkg-query -l | grep mypaint-data-extras *

You will get with mypaint-data-extras package name, version, architecture and description in a table

mypaint-data-extras package basic information: