well I don't know if it differs for debian based distros, but typically it goes a little something like this (at a terminal);
sudo init 3
sh NVIDIA-DRIVER-PACKAGE-NAME-HERE
(accept to license etc etc, install as appropriate)
sudo nvidia-xconfig (do a 'man' on this to see options it gives for setup, e.g; dual monitors etc...)
sudo init 6 (to reboot machine)