After you open a new credit card account or renew an existing credit card, you should receive a physical card in the mail. But before you can start using the new card to make purchases, earn rewards, and build your credit score, you'll need to activate it.
Whether you complete your credit card activation over the phone, use your issuer’s website, or activate your new credit card through a mobile app that you download from the app store, you should activate the card right away.