Click the Start Prompting button and move your mouse scroll wheel (on the top of your mouse) to activate scrolling.
Moving your mouse scroll wheel down will also increase the speed of prompting. Moving your scroll wheel up will slow down the speed of prompting and then reverse the direction of the scrolling text.
You can also check the invert scroll direction box (in the control panel) to reverse the direction. Then, moving your mouse scroll wheel up will activate scrolling.
If you do not have a mouse with a scroll wheel, you can also use the up/down arrow keys on your keyboard to adjust your scrolling speed and direction.
If you are using a laptop, your trackpad can act as your scroll wheel. Just make sure you have your trackpad preferences (under System Preferences > Keyboard & Mouse > Trackpad) set to allow two-finger scrolling.
Once scrolling has been initiated, use the keyboard space bar to pause/resume.