It's tough to as there's no cardholder. I've tried to no success. Someone else may have a solution, but AFAIK you can't.

 

You need to register it online on vanilla.visa.com or something

 

I heard that you add it to a PayPal account as a credit card, and then buy the donation features with PayPal, but make sure you select the Visa card as the credit card!

Again, I'm not 100% sure this is correct, this is only what I have been told. But anyway, I hope this helps! :D

 

I just tried registering with a Visa gift card and it seems like the sites are currently down:

If you go to the activation site:
https://www.giftcardmall.com/Activate.aspx

It tells you to go to this site:
https://mygift.giftcardmall.com/

It is currently under maintenance. I will try to activate later, maybe tomorrow, when the site is back up. It usually works. If this doesn't work, check out this thread:
viewtopic.php?f=7&t=28146

Also, I have moved this thread to the Help/Support subforums.

 

Gift cards always have issues with online purchases. Like one guy said you can register it, there should be a phone number on the back of the card to do so, but you still might not be able to use it with Paypal. If you like to use cash to shop online you can load your PayPal with Greendot refill cards (the money packs NOT the Visa/Mastercard ones). The money goes to your PayPal account instantly and no hassles about registering your card and whatnot. They can be bought anywhere, Walmart sells them (amongst the gift cards or in the Money Center area) and many big chain pharmacies like CVS sell them too (by the gift cards).