You can tell it to start implementing step 1. And you pick it up from there. Very natural how you would approach an expert for help, but you can always audit.
I can't provide a transcript because it's work I made for a customer and I'm bound to a clause of confidentiality.
What I did is what I use to do while starting to work on a major feature: make a list of changes, new and modified functionality, think which code and db tables I will touch and how, set constraints on the edits (eg: that API must not change, that one must be retro compatible) etc. I've been a bit pedantic because this time I had to tell it to someone else. I wrote it into a md file and asked Claude to check the code and find out if my plan was consistent with the code we were starting from. It made a list of things that I needed to detail more, added some questions and we iterated on it. Basically it's what I do myself but it happened faster.