Authors: Annie Gottlieb, Slobodan Pesic (1995)
Just follow the narrative.
You may play the game entirely in your mind, but it is strongly recommended to use pen and paper to write down (or even draw) all the details that comes to mind on each step.
When the mental image is done, you will be asked questions about it. Do not think out the details you haven't imagined earlier. You should rely only on unspoiled associations, written on paper before you saw the questions.