The way this keyboard works is through the use of virtual notes on your screen which you press and then drag and drop. This is similar to how you would learn how to play a real keyboard on your computer, only it doesn't use actual keys on your keyboard. Perfect Piano actually uses a special type of interface that makes it easy for you to navigate around your keyboard. You get used to using the keyboard over time, and you'll start to find that all your fingers actually start to feel natural rather than being a constant reminder of how to hit a key. In the beginning, as with most keyboard apps, they might seem like they'll be a little complicated, but over time you'll find that it all works better. You won't spend hours typing out a song you can't play, and if you're someone who really loves music this will be amazing means of taking yourself to that next level without having to actually leave the house.
You can download Perfect Piano from Google Play and install it onto your phone just like any other piano app. However, if you really don't know how to play a piano then the best advice I can give you is to purchase a keyboard to begin with. Learning how to play the piano is not that difficult, but learning it on your phone is very easy. This is especially helpful if you're in an area that doesn't have access to a computer, or if you're going to use the piano at work, and you might not be able to schedule a regular time to get up and walk around your office.