We will start by creating an activity for Settings:

import com.trello.rxlifecycle2.components.support.RxAppCompatActivity;

public class SettingsActivity extends RxAppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
}

Then, we will add it to AndroidManifest.xml:

<activity android:name=".SettingsActivity" />

Next, we will use PreferenceFragment by forming a SettingsFragment class inside the SettingsActivity to provide the preferences UI:

public static class SettingsFragment extends PreferenceFragment {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
    }
}

The R.xml.preferences resource doesn't exist yet, but we will create it promptly. Now we need to add a fragment to activity by calling the following:

getFragmentManager().beginTransaction()
        .replace(android.R.id.content, new SettingsFragment())
        .commit();

In the end, the whole activity is very compact:

public class SettingsActivity extends RxAppCompatActivity {
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getFragmentManager().beginTransaction()
                .replace(android.R.id.content, new SettingsFragment())
                .commit();
    }

    public static class SettingsFragment extends PreferenceFragment {
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            addPreferencesFromResource(R.xml.preferences);
        }
    }
}