How to add tutorial to a flutter app when we launch it for the first time

You can use tutorial_coach_mark library,like:

import 'package:flutter/material.dart';
import 'package:tutorial_coach_mark/tutorial_coach_mark.dart';

void showTutorial() {
    TutorialCoachMark(
      context,
      targets: targets, // List<TargetFocus>
      colorShadow: Colors.red, // DEFAULT Colors.black
       // alignSkip: Alignment.bottomRight,
       // textSkip: "SKIP",
       // paddingFocus: 10,
      finish: (){
        print("finish");
      },
      clickTarget: (target){
        print(target);
      },
      clickSkip: (){
        print("skip");
      }
    )..show();
  }

To be able to use it for the first time you need the shared_preferences package:

SharedPreferences prefs = await SharedPreferences.getInstance();
var watchedIntro=prefs.getBool('watchedIntro')??false;
if(!watchedIntro)

and when the tutorial ended set watchedIntro to true:

await prefs.setBool('watchedIntro', true);

You can try out this package, tutorial_coach_mark.