How do I use the associations that I create in Rails?

How do I use the associations that I create in Rails?

References

Reference NO 1

http://guides.rubyonrails.org/association_basics.html

Reference NO 2

http://stackoverflow.com/questions/2472982/using-build-with-a-has-one-association-in-rails

Reference NO 3

http://apidock.com/rails/ActiveRecord/Associations/ClassMethods/has_many

Reference NO 4

http://www.andrewdenhertog.com/ruby-on-rails/creating-model-associations-in-rails/

Reference NO 5

http://terenceponce.github.io/blog/2012/03/02/polymorphic-associations-in-rails-32/

Reference NO 6

http://www.slideshare.net/JamesEdwardGrayII/associations-in-rails

Reference NO 7

http://rails-bestpractices.com/posts/2-use-model-association

Reference NO 8

http://www.tutorialspoint.com/ruby-on-rails/rails-models.htm