Hi@akhtar,
You need to use the MaterialApp method to create an App. You can see the below example. It may help you.
import 'package:flutter/material.dart';
void main() {
  var x = Text(
    'Hello',
    textDirection: TextDirection.ltr,
    textAlign: TextAlign.center,
  );
  var design = MaterialApp(home: x);
  runApp(design);
}