SignIn Page

Header Block

The hero-body modal-box block need's to go below the closing hero</section>tag

<div class="hero-body modal-box">
  <div class="container has-text-centered">
    <p class="title">
      Login
    </p>
  </div>
</div>

SignIn Block

Add the containerblock after the hero-body modal-box block

<div class="container">
  <div class="modal-content">
    <div class="card listing-info">
      <span class="modal-header">Sign in with social</span>
      <header class="card-footer social">
        <a class="card-footer-item">
          <button class="button is-medium social fb">Facebook</button>
        </a>
         <a class="card-footer-item">
          <button class="button is-medium social ig">instagram</button>
        </a>
      </header>

      <div class="card-content no-top-padding">
        <div class="content">

          <div class="is-separator">
            <span class="tag is-light">Or</span>
            <hr>
          </div>

          <form action="" class="modal-form">
            <p class="control has-icon has-icon-right">
              <input type="text" class="input is-invis" placeholder="Username">
              <span class="icon is-small">
                            <i class="fa material-icons">person</i>
                          </span>
            </p>
            <p class="control has-icon has-icon-right">
              <input type="password" class="input is-invis" placeholder="Password">
              <span class="icon is-small">
                            <i class="fa material-icons">remove_red_eye</i>
                          </span>
            </p>
          </form>
          <a class="button is-success book">
                      Login
                      </a>
        </div>
      </div>
      <footer class="card-footer">
        <a class="card-footer-item">Forgot Password</a>
        <a class="card-footer-item">Signup<i class="material-icons" style="
                      font-size: 18px;
                      padding-left: 4px;
                      float: right;
                      text-align: right;
                      color: #23d160;">exit_to_app</i></a>
      </footer>
    </div>
  </div>

</div>