How to Activate Unlocked iPhone 4S :
- Before you continue, please make sure that you have Wi-Fi or active internet connection and iTunes installed on your PC.
- Remove the Original Sim card from your iPhone.
- Insert your desired Sim card, which will obviously be a micro Sim Card.
- Turn on your iPhone with new sim card, don’t do anything else.
- Connect your iPhone with PC via USB cable and fire up iTunes.
- It will automatically detect your iPhone and will activate your device by itself.
Update: Now you can make iPhone official factory unlock, you can check the details from here