Select the footage and press Command Option R (mac) or Control Alt R (PC). Be careful though as this will also reverse any keyframes applied to the layer. You can also use Time Remapping (LAYER > ENABLE TIME REMAPPING). Select the keyframes that are applied by default and time reverse them (ANIMATION > KEYFRAME ASSISTANT > TIME REVERSE KEYFRAMES). With this method any keyframes already applied to the layer will not be reversed.
John Dickinson
Motionworks
https://www.motionworks.com.au