iOS应用程序启动时如何播放开场动画

I am trying to get the code correct to play an opening animation on my iphone app I created in xcode. I want it to only play when the app launches (like angry birds) not every time I go back to the main page. I have tried several things and nothing seems to be working correctly. Can someone tell me how to correctly do this? I am trying to get the code correct to play an