You can go to Carnival's website and order a brochure which will have all the ships, routes, etc. Or, you can call the toll free no. for Carnival and order one over the phone--either way it only takes a few days to get one, or as someone said, stop by a travel agency and pick one up.
I always keep the actual brochures handy--it's easier to look at the brochure and see what's what and etc. especially when you're talking to a T.A. about
a certain cabin or location--at least it works better for me that way.