In the bottom right of the screen you will see the green and yellow icon for the exit poll. When you select the icon a second screen will come up with a sample poll already created. Simply enter in your poll question and allow the students to select out of the 5 face choices. A simple idea for more anonymity, it to place either a mobile device or notebook in a certain place in your room.
Embedded below is a GIF followed by a second YouTube tutorial.