ruby on rails - How to use the Countries gem -

i trying use countries gem, had basic questions on how incorporate gem after i've bundle-installed it.

1. do need create new controller/model access countries?
2. how create simple select drop-down show list of countries user select?
3. where countries stored? (i saw data file in gem, need clarity how bring own app)

1) don't need new controller/model access countries

2) there example app on readme page shows how use forms , dropdowns.

3) countries stores within app. believe country_select includes iso 3166 gem list of countries. can view data in countries.yaml file

if want know else, recommend looking @ example app. provides example of how use gem.