It's fairly new....so some of us haven't actually experienced the benefits yet. In most ports it is supposed to help you get through the check in process more quickly.
Obtain your booking number if you don't have it already and go to Carnival's online site.
On the left side of the page there is a section called "Your Kind of Fun". It gives you three choices...choose "booked guest". On the next page about a third of the way down - again best seen on the left is "Funpass online check in". Click on that and follow the directions. Be sure to print out the page at the end that will show you have completed the online check in - from what I hear they ask to see this in order to move you from one line to another.
I can't figure out what "fun pass" does. We filled it out, but I didn't see anything different about check-in because of it. Beyond that, if you are Category 11 or up or maybe somewhere below, you are supposed to get check-in through the "skippers club". Supposedly this is there for you because of your category level. Well, we were supposed to have "skippers club" and thought we might see signs for it at the terminal. Well, no, there were no signs. I asked someone about it and they gestured in the direction of the "long line" and to talk to someone there. Well, basically, untill you got to the front of the "long line" there was no one to talk to. When I got that guys attention and mentioned the "skippers club", be blanched(I've been reading to many novels). He went to talk to someone and we were ushered to one of the people looking at your documents. There was someone in front of us and we waited, and waited, and waited. Basically, we would have been done in the same amount of time with or without the "skippers club-express check-in". And "fun pass", I put that with the "skippers club".
When you get your documents for your cruise there are pages to fill out. When you get to the page asking for your personal information it states you can go online to complete this info. Also there is information on this at the Carnival website.