Application_Form/app/views/admin/seminar_item_contents/new.html.erb

<%= form_for @seminar_item_content, url: admin_seminar_item_contents_path, html: {class: "form-horizontal main-forms"} do |f| %>
  <fieldset>
    <%= render :partial => 'form', locals: {f: f} %>
  </fieldset>
<% end %>