This guide assumes that there is already a configured webserver sitting on port 80 waiting for localhost connections. The apache2 guide guides you through this.
root.tor./etc/tor/torrcGo to the line that contains HiddenServiceDir and HiddenServicePort, uncomment those 2 lines and set them like this:
HiddenServiceDir /var/lib/tor/4get
HiddenServicePort 80 127.0.0.1:80
Start the tor service using service tor restart
Wait for a while...
Run cat /var/lib/tor/4get/hostname. That is your onion address!