Hi, this novel/game runs on the RenPy game engine. Which is a free engine specifically designed for visual novels. It's easy to use and to get started with, especially if you want to make something simple like this.
So if you want a place to start simply download RenPy and give it an install play its test game called: The question and then open up the files to that test game and look around. change the background image change the name of the characters change what they say and slowly learn how it works.
After that press create new project inside RenPy and get to writing!
Good luck! Byeee!. :D