Did you book through a Travel Agent? They should be able to pull up the deck plans and show you the cabin. If it is designated as a handicapped cabin -- it should have a roll in shower, the room should be large enough to for a wheelchair or scooter to get around. The door to the cabin should be wide enough to allow wheelchair access.
If you need additional help, please let me know. What type of disability? There should be an emergency strobe light that blinks in case of an emergency. Have you notified the cruise line of your specific disability so they are aware of your needs?