Change the Login system without database to be with database (CodeIgniter)

This is the whole code. How i can change email and password to be dynamic stored in database and do CRUD on it I want that admin can change the email and password .

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Authentication extends CI_Controller {

    public function __construct()
    {
        parent::__construct();
    }


    public function index()
    {

        if(Auth::is_loggedin()){
            redirect(site_url('home'));
        }
        $data['title'] = 'Login';
        $data['page'] = 'auth/login';
        if ($this->input->post()) {
            $this->form_validation->set_rules('email', 'Email', 'required|valid_email');
            $this->form_validation->set_rules('password', 'Password', 'required');
            if ($this->form_validation->run() == FALSE){
                $this->load->view('template', $data);
            }else {
                /*
                    The data could have been like this if it were using a db.
                    $data = [
                        'email'=>$this->input->post('email'),
                        'password'=> hash('sha256', $this->input->post('password'))
                    ];
                 */
                

                /*
                    But i will jst use this. i'm hungry self :)
                 */
                    $data = [
                    'email'=>$this->input->post('email'),
                    'password'=> $this->input->post('password')
                    ];

                /*
                    From the /app/helpers/auth_helper.php file, the login method can be setup to talk to a database.
                    NOTE: in production, i should use a model: but as you said : basic stuff!.
                    but i'm to busy, i jst wanna create a basic stuff. :)
                    I kinda like static methods :)
                 */
                    if(Auth::login($data)) {
                        if($this->session->userdata('previous_url')) {
                            redirect(site_url($this->session->userdata('previous_url')));
                        } else {
                            redirect(site_url('home'));
                        }
                    } else {
                        $this->session->set_flashdata(ERROR, '<p class="error">Invalid Email/Password</p>');
                        redirect(site_url());
                    }
                }
            }
            $this->load->view('template', $data);
        }

        public function logout()
        {
            Auth::logout();
        }}'''