You will have to contact Carnival directly (at least in my experience this was the easiest way to go). After getting everything completed you will need to mail your certificate to Carnival by certified mail.
Hope this helps.
Sensation (without KathieLee) July 2001
Paradise (smokefree) March 2002
Valor (inaugural season) May 2005
Truimph May 2007
Fascination (1st time w/DD) May 2008
Pride (with DD & DS) November 2009
We've used gift certificates from Carnival before to purchase our cruise..
and I'm sure that the directions to use them were on there? Either on the bottom of the full page form, or on the back?
Carnival Miracle to Aruba/Curacao/Dom.Rep/Grand Turk - 3/11
Carnival Miracle to Panama/Belize/Costa Rica-1/10
Carnival Sensation to Bahamas - 8/08
Carnival Spirit to Acapulco/Zijuantenejo/Manzanillo- 2/08
Carnival Miracle to Bermuda/Newport,RI - 4/07
Carnival Legend to Jamaica/Grand Cayman- 4/04
Carnival Imagination to Barbados/Martinique/St.Maarten- 2/03
Carnival Victory to San Juan/St. Thomas/St.Croix- 2/01