$ sudo apt-get update
$ sudo apt-get install kdeplasma-addons 

kdeplasma-addons is installed in your system.

Make ensure the kdeplasma-addons package were installed using the commands given below,

$ sudo dpkg-query -l | grep kdeplasma-addons *

You will get with kdeplasma-addons package name, version, architecture and description in a table

kdeplasma-addons package basic information: