Well, if you want to write the code yourself it would be best to learn a programming language like Java(Android) or Swift(iOS). There are tons of tutorials online, online courses, apps that teach coding, coding bootcamps, college classes, etc. You can also try posting your idea on Kickstarter to raise capital, then hire a programmer to write the code for you, but this requires others to truly believe in your idea. I’ve seen many successful software developers on YouTube who are self taught, it just takes dedication.