I want to implement a chess app for Android with Stockfish.
I downloaded the Stockfish binary source code, but I don't know how to use engine
Please tell me how to use Stockfish engine for programming.
Stockfish is written in C++, so in order to call it from your Android app (which I presume is written in Java), you need to call its library via JNI (Java Native Interface). This is a rather technical task better suited for Stack Overflow; here is a question to get started.
If you encounter specific problems while doing this, you can ask a question there; in it's current form it is way too broad. Afterwards, you might need to find out which methods to call (e.g. to evaluate a certain position, or to suggest the best move). That's something we'd be able to answer here, provided that you have a very specific question.
@Glorfindel is absolutely correct (+1). To get you started, do this:
isready. Do you get anything back from Stockfish?