When you launch the app you will need to allow the camera as well as the microphone (as you will be using both). The app will then prompt you to place the grid on a flat and well lit area. At the bottom you will then see text to be read out loud. The reading will trigger the app to proceed with the story. The app does a nice job of recognizing speech; however, there is a dark circle with an arrow in it to proceed to the next part of the story if there is any issue.
Embedded below is Wonderscope's YouTube video, a few pictures of my two children (Sydney and Jack) enjoying the app, a video on their thoughts on the app.
A big shout out to Richard Byrne for discussing this the other day on his blog.