Cabins on Carnival ships do not have coffee makers. Ice is readily available in the Lido buffet restaurant, and your cabin steward will fill your cabin's ice bucket while servicing your cabin.
You can put in a room service order the day/evening before for your coffee to be delivered the next morning. Depending on the itinerary I've asked the Cabin Steward to put in a standing order for the duration of the cruise. A gratuity is in order for the room service.
The Cabin Steward will service your cabin twice daily. Once in the morning after you leave, and in the evening during dinner time. As Dave said, they will refill the ice bucket. The problem is the ice buckets aren't very big and the ice melts quickly. Here's a tip if you use a lot of ice; Bring a small "personal" size cooler along if you can. The Cabin Steward will also keep it filled with ice for you if you ask them from the start.
Welcome aboard, and congratulations on your first cruise. You've come to the right place to ask questions and get friendly helpful answers.