The app is designed to teach a few letter sounds at a time and then to build them into words before moving on to the next group. To open the next group of letters you need to watch all the green letter sound videos (and trace the letter shape after the video). When all have been completed a Hairy character appears in the bottom left corner with the words Play Game. Tap this to visit the game selection screen. Once the game has been completed the next set of letters become available.