<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<form class="form-horizontal">
<fieldset>
<legend>Acesso ao Sistema</legend>
<div class="form-group">
<label class="col-md-4 control-label" for="usuario">Usuário</label>
<div class="col-md-4">
<input id="usuario" name="usuario" type="text" placeholder="Nome do Usuário" class="form-control input-md" required="">
</div>
</div>
<div class="form-group">
<label class="col-md-4 control-label" for="senha">Senha do Usuário</label>
<div class="col-md-4">
<input id="senha" name="senha" type="password" placeholder="Senha do usuário" class="form-control input-md" required="">
</div>
</div>
<div class="form-group">
<label class="col-md-4 control-label" for="enviar"></label>
<div class="col-md-4">
<button id="enviar" name="enviar" class="btn btn-success">Acessar</button>
</div>
</div>
