Setup
<%= form_for '', url: setup_index_path do |f| %>
  <%= f.fields_for @user do |ff| %>
    <div>
      <%= ff.label :first_name %>
      <%= ff.text_field :first_name, required: true %>
    </div>
    <div>
      <%= ff.label :last_name %>
      <%= ff.text_field :last_name, required: true %>
    </div>
  <% end %>
  <%= f.fields_for @account do |ff| %>
    <div>
      <%= ff.label :name, 'Company name' %>
      <%= ff.text_field :name, required: true %>
    </div>
  <% end %>
  <%= f.fields_for @user do |ff| %>
    <div>
      <%= ff.label :email %>
      <%= ff.email_field :email, required: true %>
    </div>
    <div>
      <%= ff.label :password %>
      <%= ff.password_field :password, required: true %>
    </div>
  <% end %>
  <%= f.button button_title %>
<% end %>