To use it, you just open the app, point the camera skywards, and let the magic happen. After waiting a few seconds for the app to load, you will see the constellations begin to form on your screen. You can then learn their names, positions, etc.
Along with this function, Sky Map includes another interesting feature that allows you to locate different planets and constellations. To do so, you just have to enter the name of the planet you are looking for, for example Mars, and point your camera to the sky. The screen will then show you a circle with an arrow indicating exactly where it lies in the sky.
Sky Map is a fantastic application. It's not only educational, but also proves a great source of enjoyment on a starry night.