Storing datas of Multiple Android Users in Firebase Database

I am trying to build an Android app (Question & Answers)which has a centralized mechanism of storing the data(Marks of each user using my app).I found Firebase to be an interesting one in Realtime Database.However ,am unable to find or understand on how it can store the data separately/individualy based on each user using the app in the same database.can someone help me with brief explanation on the same?