hasmanythrough – instant CRUD for Rails

I'm going by the example at:


And would like to add an interface along the lines of the "dream" project interface at http://users.drew.edu/bburd/RubyOnRails/ . However, when I adapted this HABTM to my has_many_through I got many errors -- perhaps because of deprecated approaches.

How do I create a CRUD interface for the relationship between all three tables? Either I find no information about the CRUD operations in this context, too much information to digest, or out of date information which appears to be buggy because it doesn't apply.

I fairly faithfully followed the above guide:


and would now like to work on the CRUD interface. Is there some how-to page which I'm missing?