How to find the MAC address of the iPhone 4 so that you could use this information to connect to a Wi-Fi network where it uses MAC filtering.
1. Go to the Settings screens.
2. Next tap on General.
3. Then tap on About.
4. From the About screen you will find various information about the iPhone 4 such as storage capacity, software version and etc. Scroll down and Find Wi-Fi and Bluethooth addresses information.
See iPhone 4 User Guide Page 189 to learn more about your device.