$ sudo apt-get update
$ sudo apt-get install psi-plus-skins 

psi-plus-skins is installed in your system.

Make ensure the psi-plus-skins package were installed using the commands given below,

$ sudo dpkg-query -l | grep psi-plus-skins *

You will get with psi-plus-skins package name, version, architecture and description in a table

psi-plus-skins package basic information: