To edit schema.rb is considered to be bad practice:
...not designed to be edited, they just represent the current state of the database.
For creating a new model (and thus a new db table) call the rails model generator
rails generate model Product name:string
Or: For new fields for an existing model please generate a migration...
rails generate migration AddNameToProducts
... edit it and then run it with "rake db:migrate
"
These tasks are very well described at the official RailsGuides > Migrations