como centralizo o menu?
<!DOCTYPE html>
<html lang="PT-BR">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>NomeEmpresa</title>
<!-- link CSS Bootstrap -->
<link href="css/bootstrap-responsive.css" rel="stylesheet">
<link href="css/bootstrap.css" rel="stylesheet">
<link href="css/style.css" rel="stylesheet">
<script src="js/jquery.js"></script>
<script src="js/bootstrap.js"></script>
</head>
<body>
<nav class="navbar navbar-expand-lg navbar-light bg-light">
<a class="navbar-brand" href="#">Nome Empresa</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarNav">
<ul class="navbar-nav">
<li class="nav-item active">
<a class="nav-link" href="#">Início <span class="sr-only">(current)</span></a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Features</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Pricing</a>
</li>
<li class="nav-item">
<a class="nav-link disabled" href="#">Disabled</a>
</li>
</ul>
</div>
</nav>
<!--fim menu-->
<div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel">
<ol class="carousel-indicators">
<li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
<li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
<li data-target="#carouselExampleIndicators" data-slide-to="2"></li>
</ol>
<div class="carousel-inner">
<div class="carousel-item active">
<img class="d-block w-100" src="img/catalogo.jpg" alt="First slide">
</div>
<div class="carousel-item">
<img class="d-block w-100" src="img/frota.jpg" alt="Second slide">
</div>
<div class="carousel-item">
<img class="d-block w-100" src="img/produtor.jpg" alt="Third slide">
</div>
</div>
<a class="carousel-control-prev" href="#carouselExampleIndicators" role="button" data-slide="prev">
<span class="carousel-control-prev-icon" aria-hidden="true"></span>
<span class="sr-only">Previous</span>
</a>
<a class="carousel-control-next" href="#carouselExampleIndicators" role="button" data-slide="next">
<span class="carousel-control-next-icon" aria-hidden="true"></span>
<span class="sr-only">Next</span>
</a>
</div>
<div class="container-fluid">
<h3>Basic Navbar Example</h3>
<p>A navigation bar is a navigation header that is placed at the top of the page.</p>
<p>The navbar-expand-xl|lg|md|sm class determines when the navbar should stack vertically (on extra large, large, medium or small screens).</p>
</div>
</body>
</html>
</html>
