$ sudo apt-get update
$ sudo apt-get install gnash-cygnal 

gnash-cygnal is installed in your system.

Make ensure the gnash-cygnal package were installed using the commands given below,

$ sudo dpkg-query -l | grep gnash-cygnal *

You will get with gnash-cygnal package name, version, architecture and description in a table

gnash-cygnal package basic information: