Dear candidate

First of all you need to sketch your idea of app that you wanted to create and do research and then make graphical design and if you do not have enough knowledge about app development then attend online or offline classes for learning how to develop an app and for that you need to know JAVA programming language and make sure that you are good at programming and if you are good at those things then follow the steps given below and consult professions which improves your knowledge

1. Get an idea or a solution for a problem
2. Identify the requirement
3. Create a layout of features
4. Remove non core features
5. Create an efficient design
6. Start programming

All the best.