To give a gift there are a couple of options. You can call or email the Account Management department and request to pay for the gift (subscription time, upgrade, Premium Service). You can also email. Contact links for both can be found in my signature.
If you're calling, be sure you have:
-the last 4 digits of your credit card
-the billing address on file
-what gift you'd like to give
If you're emailing, be sure to include:
-your username (game login)
-your first and last name
-the last 4 digits of your credit card
-the billing address on file
-what gift you would like to give
Either way, you'll need to have at least two of the following for the account that you want the gift applied to:
-the name of at least 1 character & the server the character is on
-the first and last name of the account user
-the email address on file
-the address on file
-the username of the account (not recommended for privacy/security reasons)