You want to install apt-offline. It is the most convenient way to
administrate an offline system.
You would first have to:
Download apt-ofline's package from one of Taranis' mirrors:
http://packages.trisquel.info/toutatis/all/apt-offline/download
Bring it to the offline system
Install it with 'dpkg -i' or, if GDebi was installed on your system, by
double clicking on the .deb package.
Here is a documentation on the use of apt-offline.
The first package you may want to install with the apt-offline command is
"apt-offline-gui"... so that you do not have to use the command line anymore.
