Confused on how to setup Geokit

So I've searched through all the documentation on Geokit for rails and didn't find any setup process for it except for installing the gem which I know how to do. what tables do I add to an existing "listings" table?

I've like I said, have it installed. And I've added the acts_as_mappable to the listings ruby file.

class Listing < ApplicationRecord
  acts_as_mappable
end

gem 'geokit-rails'

It would be nice if there was a video tutorial done on how to set this entire thing up.