Not exactly sure how MSC does it. We were married on RCCL. Probably a similar process. First book your cruise. Then call the department of MSC that handles weddings, renewals, etc. That person (planner) will answer all your questions. They will accommodate you in anything you want to do (within reason). Be prepared to ante up for any frills beyond the basic package. While our experience on Royal was not cheap, it was very well done. My lovely wife was very happy. Very happy. Good luck.