new.html.eex

<div class="row">
  <div class="col-md-4 col-md-offset-4">
    <h1>Mango Customer Login</h1>
    <%= form_for @conn, session_path(@conn, :create), [as: :session, id: "session-form"], fn f -> %>
      <div class="form-group">
        <%= text_input f, :email, placeholder: "Email", class: "form-control" %>
      </div>
      <div class="form-group">
        <%= password_input f, :password, placeholder: "Password", class: "form-control" %>
      </div>
      <%= submit "Log in", class: "btn btn-primary" %>
    <% end %>
  </div>
</div>