According to Capital One, credit cards can be activated online as of September 2014. Users who have the card's three-digit CVV code and a Capital One online account can go to Capital One's activate page, log in to their account, and enter the CVV code to activate the card.
The Capital One website notes that if there are multiple authorized users on the account, only the account holder can activate the card. The newly activated credit card can be linked to any other Capital One accounts the card holder has. Capital One allows credit card payments to be made online manually or through automatic payments. Payments can also be made by mail or over the phone.