Go to www.greendot.com and click on "register/activate" in the top right corner of the website. Select whether your card was a gift or purchased. If your card was a gift, you only have to activate it. To do so, type in the 16-digit number on the card, the expiration date, the three-digit security code, the last four digits of your Social Security number and a security code. You also need to create a four-digit PIN. If you purchased your card, you will be prompted through a three-step registration process. Enter the 16-digit card number and the three-digit security code. Enter the activation code on the back of your package and your basic mailing information. Finally, add money to your card by transferring funds from your bank account into your new Visa Green Dot account. If you have any problems, contact a customer service representative at 1-866-795-7597.