Firstly generate a migration file.
rails g migration products title:string description:string plan:string
and then migrate it
rake db:migrate
Follow this Guide.You really need this.
Update:
Seems like you have generated an empty migration file.Now have to do
1.Open that migration file and add these lines under the def
t.string :title
t.string :description
t.string :plan
2.Do rake db:migrate
after that.