How/where can i make an app for the iphone?

Not a game just an app in general

You'd need to get access to the iOS SDK & of course have some knowledge of programming.

Use a program for Mac called Xcode, it is designed for iOS apps/games as well as WatchOS, OS X and tvOS. If you don't have a Mac then you can use http://www.macincloud.com/ which allows you to rent a Mac via the Cloud so you can use Xcode while using Windows