$ sudo apt-get update
$ sudo apt-get install iceowl-extension 

iceowl-extension is installed in your system.

Make ensure the iceowl-extension package were installed using the commands given below,

$ sudo dpkg-query -l | grep iceowl-extension *

You will get with iceowl-extension package name, version, architecture and description in a table

iceowl-extension package basic information: