It would be the same address as you send your regular payments.Call the Toll Free Number on the back of your Card from Citi., they usually have the mailing address.. You can also find the mailing address at the Citi Bank Web site..
Check this: http://consumers.creditnet.com/straighttalk/board/showthread.php?s=&postid=84860#post84860 Note that the zip code written there is wrong. The right one is 07606-8011. Saar