umm, inside it? :)
if the front of the Flic is facing you, twist it counter clockwise and it the back should open. It uses a CR2032 coin battery.
The only time I ever see a light on my Flic is when the battery is being replaced for a brief second, or when there is an error of some kind. You will see Red shine through the Flic logo. Other than that there is no light during normal operation of the button.