Hi Annette, and welcome to cruise-chat.
I think you are wise to consider flying the day prior to your cruise. As Jim mentioned, you may make these arrangements through Carnival, or on your own if less expensive.
If you go through Carnival, you might also ask them about any pre-cruise hotel packages they may have. We recently added one to our upcoming cruise (different line), and it was actually less expensive than booking directly.
Let us know how it turns out.