How to represent serialized fields in ActiveRecord::Base in ActiveRecord:Migration (Rails 2.3.16)

I'm new in rails. I read rencently how to serialize an array of string for example to store it in database.

class Fle < ActiveRecord::Base
   serialze :etat_fle

end

But i don't know how to represent this serialized field in the corresponding ActiveRecord::Migration Have someone an idea ?