Se agregó el campo Bio a 'editar perfil': se creó la migración, pero luego, ¿qué agregar al modelo?

I've followed Hartl's rails tutorials to the of Chap 9 and now i'm building my own idea so i can get deep into rails.

Current issue - I've added a Bio filed to user profiles in edit and the text box appear on the Users profile but i can't figure out how to save the text added to the Bio text box. I've generated a migration called "add_bio_to_user_profile" (haven't raked yet) but i'm struggling to figure out what to add to the User.rb model. Does controller come into this to?

Migration "add_bio_to_user_profile"

   class AddBioToUserProfile < ActiveRecord::Migration
  def change
    add_column :user_profiles, :, :string
  end
end

Model/User.rb

class User < ActiveRecord::Base

  before_save { self.email = email.downcase }
  before_create :create_remember_token

  validates :name, presence: true, length: { maximum: 50 }
  #VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i
  validates :email, presence:   true,
                    #format:     { with: VALID_EMAIL_REGEX },
                    uniqueness: { case_sensitive: false }
  has_secure_password
  validates :password, length: { minimum: 6 }

  def User.new_remember_token
    SecureRandom.urlsafe_base64
  end

  def User.encrypt(token)
    Digest::SHA1.hexdigest(token.to_s)
  end

  private

    def create_remember_token
      self.remember_token = User.encrypt(User.new_remember_token)
    end
end

controllers/user_controller.rb

class UsersController < ApplicationController
  before_action :signed_in_user, only: [:index, :edit, :update, :destroy]
  before_action :correct_user,   only: [:edit, :update]
  before_action :admin_user,     only: :destroy

def index
    @users = User.paginate(page: params[:page])
  end

  def show
    @user = User.find(params[:id])
  end

  def new
    @user = User.find(params[:id])
  end

  def new
    @user = User.new
  end

  def destroy
    User.find(params[:id]).destroy
    flash[:success] = "User destroyed."
    redirect_to users_url
  end


  def create
    @user = User.new(user_params)
      if @user.save
        sign_in @user
        flash[:success] = "Welcome to the Sample App!"
        redirect_to @user
      else
        render 'new'
      end
  end

  def edit
  end

  def update
    if @user.update_attributes(user_params)
      flash[:success] = "Profile updated"
      sign_in @user
      redirect_to @user
    else
      render 'edit'
    end
  end

  private

    def user_params
      params.require(:user).permit(:name, :email, :password,
                                   :password_confirmation)
    end

    # Before filters

    def signed_in_user
      unless signed_in?
        store_location
        redirect_to signin_url, notice: "Please sign in."
      end
    end

    def correct_user
      @user = User.find(params[:id])
      redirect_to(root_url) unless current_user?(@user)
    end

    def admin_user
      redirect_to(root_url) unless current_user.admin?
    end
end

mostrar.html.erb

<% provide(:title, @user.name) %>
<div class="row">
  <aside class="span4">
    <section>
      <h1>
        <%= gravatar_for @user %>
        <%= @user.name %>
      </h1>
    </section>

        <div>
            <textarea rows="3"></textarea>
            </div>

  </aside>
</div>

editar.html.erb

<% provide(:title, "Edit user") %>
<h1>Update your profile</h1>

<div class="row">
  <div class="span6 offset3">
    <%= form_for(@user) do |f| %>
      <%= render 'shared/error_messages' %>

      <%= f.label :name %>
      <%= f.text_field :name %>

      <%= f.label :email %>
      <%= f.text_field :email %>

      <%= f.label :bio %>
      <textarea rows="3"></textarea>

      <%= f.label :password %>
      <%= f.password_field :password %>

      <%= f.label :password_confirmation, "Confirm Password" %>
      <%= f.password_field :password_confirmation %>

      <%= f.submit "Save changes", class: "btn btn-large btn-primary" %>
    <% end %>

    <%= gravatar_for @user %>
    <a href="http://gravatar.com/emails">change</a>
  </div>
</div>