You will have to keep your carry on till they let you in your cabin. Time is Different on each ship, depends on when they get your room ready. Sometime from 1300 to 1400. Sometimes you can get to your cabin and throw it in the closet, but the room will not be locked. Up to you. Sometimes the doors are locked and you can't get there at all. Here your luggage info.
Guests are encouraged to limit their checked luggage to two suitcases per person, with each suitcase not to weigh more than 50 pounds and not exceed 16"H x 24"W x 30"L. Please attach your Carnival Cruise Lines luggage tags PRIOR to leaving home and make sure that they are still on your bags when checking in with us. In many ports, guests have the option of carrying luggage on board at embarkation and off the ship at the end of the cruise as long as it does not exceed 24"W x 16"H x 30"L. This is an advantage you may want to consider as it will allow for quicker easier access to your bags. Please note that Carnival assumes no responsibility for carry-on luggage.
Alternatively, curbside porters are available at the pier to take luggage to the vessel for delivery to your stateroom by shipboard personnel. Customary tip is $1 per bag. Please be sure each piece of luggage is unlocked and has a tag listing your name and stateroom number. Curbside porters are not employees of Carnival; therefore, if you experience any problems, please report them to porter management on site. Any luggage left at the pier will be forwarded at your expense. Claims for luggage loss or damage must be made in writing to the debarkation personnel prior to leaving the pier area.
If you are traveling by air, we strongly recommend that you contact your air carrier to obtain their luggage allowance policy for the maximum number, size and weight of bags that each guest is allowed at no charge. Guests are responsible for luggage fees, excess luggage charges as well as any other charges imposed by air carriers or airports. We recommend that each guest verify with the airline representative that their luggage is checked-in to their final destination.