Installed devise and created devise User model

app/models/user.rb

+class User < ApplicationRecord
+  # Include default devise modules. Others available are:
+  # :confirmable, :lockable, :timeoutable and :omniauthable
+  devise :database_authenticatable, :registerable,
+         :recoverable, :rememberable, :trackable, :validatable
+end

config/locales/devise.en.yml

+# Additional translations at https://github.com/plataformatec/devise/wiki/I18n
+
+en:
+  devise:
+    confirmations:
+      confirmed: "Your email address has been successfully confirmed."
+      send_instructions: "You will receive an email with instructions for how to confirm your email address in a few minutes."
+      send_paranoid_instructions: "If your email address exists in our database, you will receive an email with instructions for how to confirm your email address in a few minutes."
+    failure:
+      already_authenticated: "You are already signed in."
+      inactive: "Your account is not activated yet."
+      invalid: "Invalid %{authentication_keys} or password."
+      locked: "Your account is locked."
+      last_attempt: "You have one more attempt before your account is locked."
+      not_found_in_database: "Invalid %{authentication_keys} or password."
+      timeout: "Your session expired. Please sign in again to continue."
+      unauthenticated: "You need to sign in or sign up before continuing."
+      unconfirmed: "You have to confirm your email address before continuing."
+    mailer:
+      confirmation_instructions:
+        subject: "Confirmation instructions"
+      reset_password_instructions:
+        subject: "Reset password instructions"
+      unlock_instructions:
+        subject: "Unlock instructions"
+      email_changed:
+        subject: "Email Changed"
+      password_change:
+        subject: "Password Changed"
+    omniauth_callbacks:
+      failure: "Could not authenticate you from %{kind} because \"%{reason}\"."
+      success: "Successfully authenticated from %{kind} account."
+    passwords:
+      no_token: "You can't access this page without coming from a password reset email. If you do come from a password reset email, please make sure you used the full URL provided."
+      send_instructions: "You will receive an email with instructions on how to reset your password in a few minutes."
+      send_paranoid_instructions: "If your email address exists in our database, you will receive a password recovery link at your email address in a few minutes."
+      updated: "Your password has been changed successfully. You are now signed in."
+      updated_not_active: "Your password has been changed successfully."
+    registrations:
+      destroyed: "Bye! Your account has been successfully cancelled. We hope to see you again soon."
+      signed_up: "Welcome! You have signed up successfully."
+      signed_up_but_inactive: "You have signed up successfully. However, we could not sign you in because your account is not yet activated."
+      signed_up_but_locked: "You have signed up successfully. However, we could not sign you in because your account is locked."
+      signed_up_but_unconfirmed: "A message with a confirmation link has been sent to your email address. Please follow the link to activate your account."
+      update_needs_confirmation: "You updated your account successfully, but we need to verify your new email address. Please check your email and follow the confirm link to confirm your new email address."
+      updated: "Your account has been updated successfully."
+    sessions:
+      signed_in: "Signed in successfully."
+      signed_out: "Signed out successfully."
+      already_signed_out: "Signed out successfully."
+    unlocks:
+      send_instructions: "You will receive an email with instructions for how to unlock your account in a few minutes."
+      send_paranoid_instructions: "If your account exists, you will receive an email with instructions for how to unlock it in a few minutes."
+      unlocked: "Your account has been unlocked successfully. Please sign in to continue."
+  errors:
+    messages:
+      already_confirmed: "was already confirmed, please try signing in"
+      confirmation_period_expired: "needs to be confirmed within %{period}, please request a new one"
+      expired: "has expired, please request a new one"
+      not_found: "not found"
+      not_locked: "was not locked"
+      not_saved:
+        one: "1 error prohibited this %{resource} from being saved:"
+        other: "%{count} errors prohibited this %{resource} from being saved:"

config/routes.rb

 Rails.application.routes.draw do
+  devise_for :users
 	resources :posts
   root to: 'posts#index'
 end
\ No newline at end of file

db/migrate/20180702141545_devise_create_users.rb

+# frozen_string_literal: true
+
+class DeviseCreateUsers < ActiveRecord::Migration[5.2]
+  def change
+    create_table :users do |t|
+      ## Database authenticatable
+      t.string :email,              null: false, default: ""
+      t.string :encrypted_password, null: false, default: ""
+
+      ## Recoverable
+      t.string   :reset_password_token
+      t.datetime :reset_password_sent_at
+
+      ## Rememberable
+      t.datetime :remember_created_at
+
+      ## Trackable
+      t.integer  :sign_in_count, default: 0, null: false
+      t.datetime :current_sign_in_at
+      t.datetime :last_sign_in_at
+      t.string   :current_sign_in_ip
+      t.string   :last_sign_in_ip
+
+      ## Confirmable
+      # t.string   :confirmation_token
+      # t.datetime :confirmed_at
+      # t.datetime :confirmation_sent_at
+      # t.string   :unconfirmed_email # Only if using reconfirmable
+
+      ## Lockable
+      # t.integer  :failed_attempts, default: 0, null: false # Only if lock strategy is :failed_attempts
+      # t.string   :unlock_token # Only if unlock strategy is :email or :both
+      # t.datetime :locked_at
+
+      t.string :first_name
+      t.string :last_name
+
+      t.timestamps null: false
+    end
+
+    add_index :users, :email,                unique: true
+    add_index :users, :reset_password_token, unique: true
+    # add_index :users, :confirmation_token,   unique: true
+    # add_index :users, :unlock_token,         unique: true
+  end
+end

test/fixtures/users.yml

+# Read about fixtures at http://api.rubyonrails.org/classes/ActiveRecord/FixtureSet.html
+
+# This model initially had no columns defined. If you add columns to the
+# model remove the '{}' from the fixture names and add the columns immediately
+# below each fixture, per the syntax in the comments below
+#
+one: {}
+# column: value
+#
+two: {}
+# column: value

test/models/user_test.rb

+require 'test_helper'
+
+class UserTest < ActiveSupport::TestCase
+  # test "the truth" do
+  #   assert true
+  # end
+end