Devise gem is used to make a simple authentication solution in rails.You no need to create authentication form it will create automatically. Like Username, Password, Signin, Signup, Forgot Password and Remember me.Please follow below steps. 10 Steps for Setup Devise gem in rails application : Step 1 : Create a new Ruby on Rails Application > rails new devexam . Step 2: Open Gemfile and add the devise gem in Gemfile (devexam/Gemfile) gem 'devise' Step 3: Install newly added gem > bundle install Step 4: Create the Product form with CRUD using scaffold > rails g scaffold Product name:string price:integer description:text Step 5: Apply changes to database.Product table added to database with help of migration. > rake db:migrate ...