app/views/devise/invitations/new.html.erb
<h2>Send invitation</h2>
<%= form_for resource, :as => resource_name, :url => invitation_path(resource_name), :html => {:method => :post} do |f| %>
<%= devise_error_messages! %>
<p><%= f.label :email %><br />
<%= f.text_field :email %></p>
<p><%= f.submit "Send an invitation" %></p>
<% end %>
<%= link_to "Home", after_sign_in_path_for(resource_name) %><br />