Bootstrap Form Navbar pour ajouter une nouvelle ligne

<nav class="navbar navbar-toggleable-md navbar-inverse bg-inverse">
    <div class="container">
        <button class="navbar-toggler navbar-toggler-right align-self-center mt-3" type="button" data-toggle="collapse" data-target="#navbarCollapse">
            <span class="navbar-toggler-icon"></span>
        </button>
        <h1 class="py-2 ml-lg-2 mx-3"><a href="#"><i class="fa fa-envelope-open-o fa-lg" aria-hidden="true"></i></a></h1>
        <div class="collapse navbar-collapse ml-lg-0 ml-3" id="navbarCollapse">
            <ul class="navbar-nav">
                <li class="nav-item active">
                    <a class="nav-link" href="#">Home</a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="#">Product</a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="#">Shop</a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="#">About</a>
                </li>
                <li class="nav-item">
                    <a class="nav-link" href="#">Events</a>
                </li>
            </ul>
            <ul class="navbar-nav">
                <li class="nav-item">
                    <a class="nav-link pr-3" href="#"><i class="fa fa-facebook"></i></a>
                </li>
                <li class="nav-item">
                    <a class="nav-link pr-3" href="#"><i class="fa fa-instagram"></i></a>
                </li>
                <li class="nav-item">
                    <a class="nav-link pr-3" href="#"><i class="fa fa-twitter"></i></a>
                </li>
            </ul>
        </div>
    </div>
</nav>
Gorgeous Gnu