session login hashed password

[muntago Richard]

during registeration, i hashed and salt password using SHA 512

as follows

    // Create a random salt
    $salt = hash('sha512', uniqid(mt_rand(1, mt_getrandmax()), true));
    // Create salted password (Careful not to over season)
    $pass = hash('sha512', $pass.$salt);

salt and pass are stored in database. but i don't know how to create login form using hashed and salted password. can anyone help me below is my login form

<?php
//session_start();

if (
    isset($_POST['username']) &&
    isset($_POST['pass']) &&
    !empty($_POST['username']) &&
    !empty($_POST['pass'])
) {

    $db = new PDO(
        'mysql:host=localhost;dbname=timeline', // dsn
        'root', // username
        '' // password
    );

    $statement = $db->prepare('
        SELECT * FROM users
        WHERE username = ?
        AND password = ?
    ');

    $statement->execute(array(
        $_POST['username'],
        $_POST['pass']
    ));

    if ($row = $statement->fetch()) {
    
        $_SESSION['sess_userid'] = $row['uid'];
        $_SESSION['sess_name'] = $row['username'];
        include('success.php');
        
    } else include('fail.php');
    
} else include('fail.php');

?>