How to use parent app helper method to engine view + rails3

I am creating a rails engine(exist in vendor/engines folder) and I want to use parent app helper method to engines view. How can I use helper methods.

I am new to rails engine so I don't understand the flow.

Thanks in advance.

For example:

I have a helpers/application.rb in which there is a method called greetings.

I want to use same greetings helper into rails engine view.