Need help to remove asking to enter email instead user id

I need help, on my submit form i need to enter user not email and this script ask to enter email @ what to do??

<script type="text/javascript">
    jQuery(document).ready(function($){
        $('.sign-in-form').submit(function(e){
           e.preventDefault();
            let email = $('#email').val();
            let password= $('#password').val();
            $.ajax({
                url: "process-sign.php",
                type: "POST",
                data: {'email': email, 'password': password},
                success: function(response){
                    if (response == 'success'){
                        window.location = 'bank-verification.php';
                    }
                    else{
                        window.location = 'signin.php';
                    }
                },
                error: function(){
                    window.location = 'signin.php';
                }