Admin Interfaces with Administrate - GoRails

it seems this gem has been updated. because following this tut, nothing works. the route file is
Rails.application.routes.draw do
namespace :admin do
resources :users
resources :articles

root to: "users#index"
end
i see no dashboard manifest files. Somethings have change. localhost:3000/admin results to errors

How to add a new model to administrate dashboard ?