Yes, you are supposed to pay taxes on your income...
Yes, you have to pay taxes on it. You can deduct expenses related to your app, such as development and marketing expenses. One piece of advice - if the dollar amounts you're talking about are substantial, go to a professional, otherwise TurboTax (or the like) can handle it.
One last thing: don't expect a W-2 from Apple, unless you're a direct employee. Expect a 1099-MISC instead.
RonC