The website address for activating a prepaid MasterCard is available on the packaging that came with the prepaid card, according to MasterCard. Owners of prepaid MasterCards can also call the phone number provided on the packaging to activate their cards.
Activation and registration requirements vary with different types of MasterCards. Registration of a prepaid card is required to be able to reload credit onto the card or to request a replacement card. Registration requires providing personal information to MasterCard, though activation does not. Prepaid MasterCards can be used at any retailer that accepts MasterCard debit cards, as MasterCard explains. Because retailers can't provide card balances, users of prepaid cards should be aware of their balances before shopping.