Your card is ready to use immediately for online and Chip & Pin transactions. You won't need to activate it. To enable contactless just make one Chip & PIN transaction at point of sale. Point of sale is when you pay for goods or services in a shop, you'll need to insert your card into the retailers card machine and complete the payment.
You can view your card details any time in the app, for more information, check out this article.
You can also add your card to your mobile wallet e.g. Apple/Google pay. For instructions on how, check out this article.