I have an iphone. I just bought an At&t sim card and a 50 dollars refill card. How do I activate it?

I have an iphone. I just bought an At&t sim card and a 50 dollars refill card. How do I activate it?

Put the SIM in the phone and follow the instructions.

You do realize that the instructions are on the back of the refill card as well as on the packaging that came with your SIM card, right?