I have just completed the transition myself. I had 200 hours fixed-wing and an FAA ME CPL (A) from a few years ago, so my case was not straight forward.
Basically I had to do the 5 ATPL exams, training as required to pass the CPL test which must include a full MEP course (min 6 hours) and a 10 hour IR conversion.
This course of training had to approved by my licensing authority after receiving a training recommendation from an ATO.
Hope it helps.