Errors while creating my first app

Hello, i am a complete beginner, i downloaded and installed the composer mentioned in the official website and followed all the steps but the problem is when i created my first app “myapp” and used the link http://localhost:8765/myapp i got these messages :
“Error: MyappController could not be found.”
“Create the class MyappController below in file: src\Controller\MyappController.php”
"<?php
namespace App\Controller;

use App\Controller\AppController;

class MyappController extends AppController
{

}

I did it and i got this message
"Create MyappController::index() in file: src\Controller\MyappController.php.”

"

<?php namespace App\Controller; use App\Controller\AppController; class MyappController extends AppController { public function index() { } } " I also did that but i got these messages "Confirm you have created the file: "Myapp\index.ctp" in one of the following paths" and "If you want to customize this error message, create src\Template\Error\missing_template.ctp" and now i don't really know what to do or what to write in that file even if i create it

You should visit http://localhost:8765 not http://localhost:8765/myapp

It’s most likely that littleylv is right. The messages you got says it’s using “http://localhost:8765/” as the root of the application. Inside that application it’s attempting to find a controller called myapp.