I have attended two weddings on the Carnival Victory. Both took place at 1PM on the ship in Miami the day of cruise departure. The wedding will be held in one of the lounges on the ship. Depending on the size of your wedding group and how many other weddings they have the day of your departure will determine which lounge. Both weddings I attended were small about 30 people or less. The room is set up to form an aisle coming in from the lounge door, leading to where the bride and groom will stand. On each side where they stand is white column stands with flowers. The guest chairs are on each side. The ships photographer will be taking all the traditional pictures. The officiate will perform the ceremony (unless you have made arrangements for a specific pastor, reverand, etc. The ceremony itself is probably only about 20 minutes. What happens next is dependent on which wedding package you buy. One wedding we stayed in the same lounge and had a champagne toast and cake. The other wedding was larger and they bought the one hour reception. For that we moved to the Disco lounge where they had hot and cold hordourves, and one hour of cocktails. They had decorations and ice sculpture set up in the Disco.
Warning: The photographer can get carried away after the ceremony taking up your time wanting to take way too many pictures. Ofcourse they are hoping you will buy them all. If you find this happening, politely tell them "Thank You, that's enough"
Hope this helps.