Build the app

• create a new directory "menu" under "views/devise/menu/"
• create a new file, call it: "views/devise/menu/_login_items.html.erb"

file content:
<% if user_signed_in? %>

<%= link_to('Logout', destroy_user_session_path, :method => :delete) %>

<% else %>

<%= link_to('Login', new_user_session_path) %>

<% end %>

as described in: https://github.com/plataformatec/devise/wiki/How-To:-Add-sign_in,-sign_out,-and-sign_up-links-to-your-layout-template

• add to the file: views/layout/application.html.erb the following content:

  <%= render :partial => 'devise/menu/login_items' %>