update multiple model in one form

my project works like this the user will sign up first.after sign up he/she will edit his profile.I use restful authentication plugins for sign up. model class User < ActiveRecord::Base   has_one :profile end

class Profile < ActiveRecord::Base   belongs_to :user end

user controller def create   cookies.delete :auth_token   @user = User.new(params[:user])   @user.save

  @profile = Profile.new   @profile.user_id = @user.id   @profile.save end    def edit     @user = User.find(params[:id])    end

migration class AddProfileTable < ActiveRecord::Migration   def self.up     create_table :profiles do |t|       t.string :lastname       t.string :firstname       t.integer :user_id

    end   end

  def self.down     remove_table :profiles   end end edit form <h1>Editing user</h1>

<%= error_messages_for :user %>

<% form_for(@user) do |f| %>

<p>     <b>Name</b><br />     <%= f.text_field :login %>   </p>

  <p>     <b>Email</b><br />     <%= f.text_field :email %>   </p>

   <p>     <%= f.submit "Update" %>   </p> <% end %>

my problem, how to add the lastname and firstname on the form and update the model profile?and what the method update?