$ sudo apt-get update
$ sudo apt-get install irssi-plugin-xmpp-dbg 

irssi-plugin-xmpp-dbg is installed in your system.

Make ensure the irssi-plugin-xmpp-dbg package were installed using the commands given below,

$ sudo dpkg-query -l | grep irssi-plugin-xmpp-dbg *

You will get with irssi-plugin-xmpp-dbg package name, version, architecture and description in a table

irssi-plugin-xmpp-dbg package basic information: