First of all, run this command with oldname is the attribute that you like to change and newname is the attribute you like to replace

rails g migration change_oldname_to_newname

Look for the file ….. in ….. and modify like the following

class change_oldname_to_newname <ActiveRecord::Migration

def change     rename_column :table_name,:old_column,:new_column   end
end

Save the changes and update these change by running this comand

rake db:migrate

Those steps will do the steps.