ruby on rails - Is it possible to add authentication with devise if a model is already present? -

i have added devise in gemfile , did bundle install..now how can give authentication sage created?

this controller sages.rb

class sagescontroller < applicationcontroller   def home   end    def   end    def new     @sage = sage.new   end    def create     @sage= sage.new(sage_params)     if @sage.save       flash[:success] = 'thanks joining'       redirect_to '/thanks'     else       flash[:notice] = 'please fill form correctly'       render 'new'     end   end    def edit     @sage=sage.find(params[:id])   end    def update     @sage = sage.find(params[:sage])     if @sage.update_attributes(sage_params)       redirect_to '/thankss'     else       render 'new'      end end     def resources    end    private   def sage_params     params.require(:sage).permit(:name, :email, :address, :number)   end end 

this new.html.erb in sage created

<div class="contact" style="padding: 50px; color: orange ">    <%= form_for @sage |f|  %>        <div class="form-group" >         <h3><%= f.label :name%></h3>         <%= f.text_field :name %>         <br/>       </div>       <div class="form-group" >         <h3><%= f.label :email%></h3>         <%= f.email_field :email %>        </div>       <div class="form-group" >         <h3><%= f.label :address%></h3>         <%= f.text_field :address %>         <br/>       </div>       <div class="form-group" >         <h3> <%= f.label :number%></h3>         <%= f.number_field :number %>         <br/>       </div>       <br/>       <br/>       <div class="submit" >         <h2><%= f.submit 'submit'%></h2>       </div>      <% end %>  </div> 

this routes.rb

  '/thanks'=> 'users#thanks'   '/thankss'=>'users#thankss'   '/thanksss'=>'users#thanksss'   resources :sages,only: [:new,:create,:edit, :update, :delete, :destroy]   '/sages/edit/:id'=>'sages#edit'   'sages/home'=>'sages#home'   'sages/about'=>'sages#about'   'sages/resources'=>'sages#resources'   'sages/delete/:id'=> 'sages#delete'   delete 'sages/delete/:id'=> 'sages#destroy' 

add following line controller,

before_action :authenticate_user! 

or follow this.