Are you talking about the psychotherapist in emacs? If so, I'm assuming you mean type to it, not actually speak to the computer.
Once you are in emacs, you can get it by going to the help menu, and I believe it is option P.
So the sequence of commands would be
M-` (to open the menu)
h (to go to the help menu)
P (to open the psychotherapist)
Incase it isn't obvious, M- means hold the meta key.