How do I implement a Scrollview for java?

Question

(I'm using Android IDE for this and I'm new to java)

I made a layout for my emulator that works in portrait mode. But I want to know how to implement a Scrollview code so that my layout works in landscape as well. Must I add something to my layout, my code, or both? I added my code below

public class MainActivity extends AppCompatActivity {

String tag = "button pressed";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    User myUser = new User("john", "abc", 123, false);

    Button myFollowButton = findViewById(R.id.followButton);

    myFollowButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            TextView followText = findViewById(R.id.followButton);

            if (myUser.isFollowed() == false){
                myUser.setFollowed(true);
                followText.setText("Unfollow");
            }
            else{
                myUser.setFollowed(false);
                followText.setText("Follow");
            }

            Log.v(tag, String.valueOf(myUser.isFollowed()));
        }
    }
    );

    ScrollView scrollView = ;
}
}