I have two models, links and tags, associated through a third, link_tags. The following code is in my Link model.
Associations:
class Link < Acti
You need to build a tag in your controller or in the view
def new @link = @current_user.links.build @link.tags.build end #in your view you can just use the association name <% f.fields_for :tags do |tag_form| %>