Hey! So you have a 1.11 mod and want to have a go at supporting MCMultiPart 2? Great! Let's get started!
I should first of all note that the API is NOT final, though the changes to it won't be very big and most likely won't affect you. Still, I would recommend doing this in a separate branch.
The first thing you'll want to do is add MCMP to your dev environment. You can read about that here: https://github.com/amadornes/MCMultiPart/blob/1.11/README.md
You'll need to use experimental builds because there is no stable build yet.