Ruby on Rails

I am trying to create a form that updates 2 tables in my database. I'm not quite sure how to build this contact form quite yet. So my first short term goal is to simply update my `contact_requests` and `users` tables. I am aiming to do a `one to many` relationship between `users` and `contact_requests`. This allows one `user` to have many `contact_requests`. I am new to rails so I feel like there are gaps in my code and I am making some mistakes as well.  Ideally, I will want to include a mailer in the form as well but one step at a time.

I currently have a `user` table and a `contact_request` table: 

`user_id` from the `contact_requests` table is a foreign key that references `users.id`

Here is by current schema code:

    ActiveRecord::Schema.define(version: 20141127114323) do

      create_table "contact_requests", force: true do |t|

        t.datetime "created_at", null: false

        t.datetime "updated_at", null: false

        t.string   "message",    null: false

        t.integer  "user_id"

      end

    

      add_index "contact_requests", ["user_id"], name: "index_contact_requests_on_user_id", using: :btree

    

      create_table "users", force: true do |t|

        t.datetime "created_at",   null: false

        t.datetime "updated_at",   null: false

        t.string   "first_name",   null: false

        t.string   "last_name",    null: false

        t.string   "email",        null: false

        t.string   "phone_number"

      end

    end

Here are my models and controllers:

    class User < ActiveRecord::Base

      has_many :contact_requests

      # validate the presence of the attributes

      validates(:first_name, presence: true)

      validates(:last_name, presence: true)

      validates(:email, presence: true)

    end

    class ContactRequest < ActiveRecord::Base

      belongs_to :user

      validates :user_id, presence: true

      validates :message, presence: true, length: { maximum: 500 }

    end

    class ContactController < ApplicationController

      def new

      @user = User.new

      @contact_request = ContactRequest.new

      end

    end

I am getting this error:

form:

    <%= form_for(:contact, remote: true, class: "contact-input") do |f| %>

          <div class="col-md-12">

            <div class="col-md-6">

              <div class="contact-input-margin form-group">

                <%= f.text_field(:user, :first_name, class: "form-control", placeholder: "First name")%>

              </div>

              <div class="contact-input-margin form-group">

                <%= f.text_field(:user, :last_name, class: "form-control", placeholder: "Last name") %>

              </div>

              <div class="contact-input-margin form-group">

                <%= f.email_field(:user, :email, class: "form-control", placeholder: "Email") %>

              </div>

              <div class="contact-input-margin form-group">

                <%= f.telephone_field(:user, :phone_number, class: "form-control", placeholder: "Phone number") %>

              </div>

            </div>

            <div class="contact-input-margin col-md-6">

              <div class="form-group">

                <%= f.text_area(:contact_request, :message, class: "form-control contact-margin", rows: "8", placeholder: "Message...") %>

              </div>

            </div>

          </div>

          <%= f.submit(class: "btn btn-xl") %>

        <% end %>