if you were approved for a credit card after you sent your credit card application, it doesn't mean you can use it right off. You should activate it, using the activation number your bank should provide in a letter, by phone or by Internet. You should also have the PIN of the credit card, which you can be given in a letter, or by phone, when you will activate your credit card.
Some people try to use the card without activating, as they already can give the card number where it is needed, but as there is no money available on the card, no payments can be processed. In some cases, there is a setup fee required to start using the credit card.
Disclaimer: This editorial content is not provided or commissioned by the credit card issuer(s). Opinions expressed here are the author's alone, not those of the credit card issuer(s), and have not been reviewed, approved or otherwise endorsed by the credit card issuer(s). Reasonable efforts are made to present accurate information, however all information is presented without warranty. Consult a card's issuing bank for the terms & conditions.
All rates and fees, and other terms and conditions of the products mentioned in this article/post are actual as of the last update date but are subject to change. See the current products' Terms & Conditions on the issuing banks' websites.