$ sudo apt-get update
$ sudo apt-get install gnome-session-flashback 

gnome-session-flashback is installed in your system.

Make ensure the gnome-session-flashback package were installed using the commands given below,

$ sudo dpkg-query -l | grep gnome-session-flashback *

You will get with gnome-session-flashback package name, version, architecture and description in a table

gnome-session-flashback package basic information: