如何将默认设置设置为NSUserNotificationAlertStyle警报通知

I am new to iOS. The app I am working on has in Settings under Notification Center the Alert style set by default to Banners. I would like to change that to Alerts. How can I do that? After doing some search on google i found that this should be changed from Info.plist using NSUserNotificationAlertStyle.I am new to iOS. The app I am working on has in