Develop photo apps using Objective-c

First of all, i want to clarify that i'm just a beginner in building iOS app.

I have a project in hand which is to build an iOS app that store images. One of the functionality of the app is to crop the image. The function is similar to the link below.(http://ift.tt/1KbLyhQ)

Can you guys guide me where should i started?

I appreciate and thank you for who visit this question.