Not sure where to post this so chit chat seems like a safe bet.
I want to develop a story with Twine which I will eventually put on an app and let people download for free.
I wanted to know how it should be configured through Twine 2 to make use of push notifications? like in lifeline for example, every text that appears on screen is sent to you as a push notification when you're not focused on the app at the moment. How do you do that?
There are at least four issues in your question which are not trivial to solve.
1. Converting a story HTML file generated by Twine into a Mobile App.
You have two basic choices if you want to create a Hybrid Mobile App:
1a. Learn how to write a native web wrapper for the mobile operating system(s) you plan to target, each one uses a different programming language and development environment.
1b. Use one of the hybrid frameworks like Apache Cordova or PhoneGap which supports both iOS and Android as well as a couple of other mobile operating systems.
2. Obtaining a Apple Developer ID if you plan on releasing your story on iOS, you will also need to get approval to actually release your story on the App Store once you have a working copy.
3. Creating the server back-end needed to push the notification messages to your app, this code is different for each mobile operating system you plan to support.
4. Implementing the functionality needed for the app to be able to receive a push notification, this code is different for each mobile operating system you plan to support.