How do you make your dad buy you an app?

The easiest way would probably be to wait for your next birthday or Christmas (if your family celebrates it) to come up and ask for it. If you're willing to work hard, you may be able to get your father to agree to buy it if you do something to earn it, like taking on more chores around the house, improving your grades at school, and paying a part of the price yourself with money earned doing work for neighbors.