There is no sign up anymore. Zette has moved the classes to the link she included above, and they're done independently now. You can also get them from Amazon for Kindle, and there may be other venues that I haven't caught up with yet.
First of all, just have to say- your 2YN techniques are great!
I just finished the first set of 2YN- it's been a great tool for getting my scatter brained thoughts down on paper for my first novel that I'm working on. Thank you for the resource! I was looking for the next set on Amazon, do you know when it will be available?