How can I get a text from a textbox and display it in a label of another C # WPF? [closed]

I have the doubt of how to put the text that is entered in a textbox in another window.

Explaining this:

The user will login in a window, at the time of entering a splash will open welcoming, what I want to do is to appear the username you entered in the splash welcoming.

My code is as follows:

Login window

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void BtnIngreso_Click(object sender, RoutedEventArgs e)
    {

        //Validacion de usuario y contraseña
            if (txtuser.Text == "User" && txtpass.Password == "1234")
            {
                //Si el usuario es correcto, llamar al splash
                SplashBienvenida splashBienvenida = new SplashBienvenida();
                splashBienvenida.LUser = txtuser;
                splashBienvenida.Activate();
                splashBienvenida.Show();
                this.Close();
            }
            else
            {
                //Mostrar el mensaje en caso erróneo 
                MessageBox.Show("Usuario o contraseña no validos");
            }

    }

Splash Window

public partial class SplashBienvenida : Window
{
    DispatcherTimer dT = new DispatcherTimer();

    public SplashBienvenida()
    {

        InitializeComponent();
        //Inicia el conteo que durara la ventana de Bienvenida
        dT.Tick += new EventHandler(dT_Tick);
        dT.Interval = new TimeSpan(0,0,10);
        dT.Start();


    }
    //Al momento que termine el conteo mandara llamar la ventana siguiente
    public void dT_Tick(object sender, EventArgs e)
    {

        Opciones opciones = new Opciones();
        opciones.Show();

        dT.Stop();
        this.Close();
    }

}