Hi mdluvs2shop, welcome to Cruise-Chat! Congratulations on your first cruise! Just be warned cruising is addictive
You and your sister are in for a marvelous time. As Dave stated, your luggage fits well under your beds.
You will get a newsletter in your cabin every evening that will outline the days events. You can do as much or as little as you want. The one thing is, you probably can't do all of it. They have so many wonderful activities. Plus, you have your ports of call.
Best wishes and once again, welcome aboard!