$ sudo apt-get update
$ sudo apt-get install cyrus-nntpd 

cyrus-nntpd is installed in your system.

Make ensure the cyrus-nntpd package were installed using the commands given below,

$ sudo dpkg-query -l | grep cyrus-nntpd *

You will get with cyrus-nntpd package name, version, architecture and description in a table

cyrus-nntpd package basic information: