Hi Rushi...

1. Choose one major platform
The major platforms in mobile app development world are Android, iOS, and Windows.

2. G et required training and education
Getting a formal training and education in software development processes is indeed required.
A degree in computer science and software engineering is a good foundation, because it helps you get a grasp on key concepts of data structuring, designing, and programming.
But even if you have passed the graduation age and still struggling where to begin with, you can opt for online courses. There are several web platforms which offer online courses specifically in app development.

3.