open sim card

Install a physical SIM

1. Insert a paper clip or SIM eject tool into the small hole of the SIM tray, then push in toward iPhone to eject the tray. ... 
2. Remove the tray from iPhone.
3. Place the SIM in the tray. ... 
4. Insert the tray back into iPhone.
5. If you previously set up a PIN on the SIM, carefully enter the PIN when prompted.

Set up cellular service on iPhone - Apple Support (IN)