Ruby on Rails paperclip questions

I want to use paperclip to upload files to server. Errors are all cleaned now, but I don't know how to set the upload path.

My code looks like this:

upload class:

  puts has_attached_file :image, :default_url => :file_system
  validates_attachment_content_type :image, :content_type => [:image,    'audio/mpeg', 'application/mp3', 'application/octet-stream']

I want that uploads are saved in project/public/uploads

how can I realise this?