Add calendarik to your Gemfile:
gem 'calendarik', :git => 'https://github.com/briu/calendarik.git'
bundle install
bundle exec rails g calendarik:event_model ModelName custom_field_str:string custom_field_int:integer
bundle exec rake db:migrate
Now you can use calendar on path /fetch_event/model_name/events
By default event form use only event fields, you can add your custom fields to form with partial, located in /shared/events/model_name.html.erb
Custom config rules for fullcalendar plugin should be stored in config/calendarik.yml