You can activate a rewards card online, though many rewards cards will be automatically activated upon the first purchase. Some stores require the card be activated before it can be used, and this is often done online using an activation code that is either emailed or mailed to the recipient.
To activate the card online, a code printed on the card or an activation code that is emailed or mailed will be needed during the process. It may be necessary to select a PIN that is needed when using the card to purchase items. Protect the reward card by signing the back of the card, and keep the PIN in a secure location.