Before doing the exercise, you should read The gist of the matter.
The narration begins with the phrase "I am an object" and then you go on to tell about yourself as though you were that object.
The Announcer says: "Watermelon"
The Object-Spokesperson says: "I am a watermelon. On the outside I am green, and inside I am pink. When I get ripe, my insides turn red and get juicy and sweet..."
You speak, and the partner listens, then you switch roles for the next word.