Hi Dagnachew,
Depending on how "new" you are to the platform, you will want to follow some guided paths to at least grab the main concepts.
Firebase component for instance has step-by-step documentation on how to setup and if you install the demo application, generate the app and install it on your phone you should be able to see it working.

Then, you can analyze the code and the documentation on how to setup and implement it on your application and use case.
Regards,
João