This is something you do on your own.
I already moved your last request into the appropriate forum under: Ocean Cruise Lines Roll Calls - Carnival Cruise Lines - Carnival Spirit 16 Feb 2013. This way you have a place to chat with other cruisers going on that cruise.
Now you just need to go to the Roll Calls & Events link at the top of the page, click on it and a menu will show, select Current Roll Calls from there it should step you through the process of seeing if a roll call for your cruise already exists and if it doesn't it will step you through the process of starting one up.
When it asks for Forum Link, enter the link to your chat forum that has already been set up (copy from link below):
If you have any issues just come back here to ask them. I will post a tutorial on this later today. I'm sure others have had similar questions.