Hi i just activated smarty card. With a pack i recived second sim. How can i activate it?

You'll have to log out of your account and go to smarty.co.uk/activate. 

There's a video here on how you can do it 🙂 https://community.smarty.co.uk/t5/help-videos/activating-a-spare-bonus-sim-or-a-sim-bought-in-a-shop-or-other/ba-p/26238