I need help creating the send email function in php

Question

<div class="container" id="fh5co-contact">
  <div class="fh5co-spacer fh5co-spacer-sm"></div>

  <div class="col-md-12">
    <div class="fh5co-section-heading">
      <h2 class="text-muted">Preencha com seus dados abaixo</h2>
      <h3 class="text-center">O que for discutido aqui, estará em sigilo.</h3>
    </div>
    <form method="POST" action="processar.php">
      <div class="col-md-6 col-md-offset-3">
        <div class="form-group">
          <label for="name">Seu nome:</label>
          <input type="text" id="name" class="form-control input-lg" placeholder="Nome e Sobrenome">
        </div>
        <div class="form-group">
          <label for="email">Email</label>
          <input type="text" id="email" class="form-control input-lg" placeholder="Seu Email">
        </div>
        <div class="form-group">
          <label for="message">Sobre o que quer falar?</label>
          <textarea name="message" id="message" cols="30" rows="10" class="form-control input-lg" placeholder="Escreva aqui"></textarea>
        </div>
        <div class="form-group text-center">
          <input type="submit" value="Enviar" class="btn btn-primary btn-lg">

        </div>
      </div>
    </form>
  </div>

</div>