When starting Navigation Drawer enter with a fragment directly

it's just that, I'm creating an app which has a login (main activity) and a record, when I pass this process, I enter a Navigation Drawer activity I have the fragments but it is blank, when I step on it the options of that menu are loaded the fragments of correct form, my problem is that I want that it opens already with the fragment of beginning and that does not load in white. if you need me to add something I will do it immediately (it's worth noting that I'm totally new in both this android and on the web but I hope to learn to also help others: D)

package company.viral.organizadorjec;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import company.viral.organizadorjec.Fragment.AjustesF;
import company.viral.organizadorjec.Fragment.CalendarioF;
import company.viral.organizadorjec.Fragment.InicioF;
import company.viral.organizadorjec.Fragment.PerfilF;
import company.viral.organizadorjec.Fragment.ProfesoresF;

public class Menucentral extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_menucentral);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menucentral, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    FragmentManager fragmentManager = getSupportFragmentManager();

    if (id == R.id.nav_camera) {
        fragmentManager.beginTransaction().replace(R.id.contenedor,new InicioF()).commit();
    } else if (id == R.id.nav_gallery) {
        fragmentManager.beginTransaction().replace(R.id.contenedor,new ProfesoresF()).commit();
    } else if (id == R.id.nav_slideshow) {
        fragmentManager.beginTransaction().replace(R.id.contenedor,new CalendarioF()).commit();
    } else if (id == R.id.nav_manage) {
        fragmentManager.beginTransaction().replace(R.id.contenedor,new AjustesF()).commit();
    } else if (id == R.id.nav_share) {
        fragmentManager.beginTransaction().replace(R.id.contenedor,new PerfilF()).commit();
    } else if (id == R.id.nav_send) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

}