I want to build ab app , from where I have to start. :-?

Answer 1

We can start on two things. The design, and the thing we are supposed to do. By the way, l cannot start, 'cause I'm on level two.
:P

Answer 2

What goal do you have? Witch app are we making? What are we supposed to do?

Answer 3

What app would you like to build?
What exactly the app have to do? (purpose, goal)
Which language is good for this purpose?
What algorithm are you going to use to reach the goal?
Find answers to these questions, then start coding.