Dina has got it exactly correct. You'll have to go to the "lifeboat drill" and that happens usually right after sailing. There will be announcements, and on the back of your cabin door it'll tell you where you need to go for that experience. Don't stress over it, as it's a necessary event. Just visit with those around while waiting for the announcements, and take pictures of each other in your life jackets.
If you board the ship very early, you probably won't be able to get into your cabin. They usually open those up somewhere around 1:30 in the afternoon. If that's the case, just head up to the Lido deck, and enjoy a leisurely lunch. Above all,,,,HAVE FUN.