[O] first step of newbe: *TODO

[Renato]

Hi,
as I already told, I'm a really newbe (to org-mode, as well as emacs)
I'm starting from the very beginning:
following the Doc (here: 
http://orgmode.org/worg/org-tutorials/orgtutorial_dto.html)
I wrote my firs TODO list.
But when I press C-c C-t over a TODO element, it appear DONE, write near 
the task, but not the CLOSED [time...] on the line after that.

What I have to do?

TIA

Renato

ps
sorry, for the stupid question, but it is really my very firs experimet :-(