$ sudo apt-get update
$ sudo apt-get install greenbone-security-assistant 

greenbone-security-assistant is installed in your system.

Make ensure the greenbone-security-assistant package were installed using the commands given below,

$ sudo dpkg-query -l | grep greenbone-security-assistant *

You will get with greenbone-security-assistant package name, version, architecture and description in a table

greenbone-security-assistant package basic information: