The helicopter is stored in a hold under the bow deck, and is raised by a hydraulic system to get it out for use. They lifted it part way, then connected the two rotor blades that go at right angles to the fore and aft ones, then raised the whole lot up to deck level, where the base forms part of the helipad.
Serene is ranked #13 ( by length ) of the largest 100 Megayachts on the Superyacht Times website.

Good set of this huge toy, Nigel.

This one shows the length most clearly, and the chopper on the bow!!