When you launch the experiment you will need to enable the camera. You will see that there are three GIFs that are loaded and ready for you. If you would like to adjust them, simply select the GIF and search for the GIF you are looking for.
When you are ready, make the facial expression, movement, etc. that you would like a GIF to trigger and hold down Train Green. When ready, change your expression/movement and select Train Purple, and finally Train Orange.
Embedded below is a GIF followed by a 1 minute and 59 second YouTube tutorial.