Download standard Linux source package here then tar xzvf gmail-notify-1.6.1.1.tar.gz in the directory you downloaded Gmail Notifier to then go into the created directory with the files and start the notifier with ./notifier.py Download a Debian package here (Deprecated) then dpkg -i gmail-notify-1.6.deb in the directory you downloaded to and type 'notifier' at an X Windows shell to start the noti