Here is how to do it:
1. Tap on the Settings icon from your iPhone 5 home screen.
2. From the Settings menu, locate and tap on Wi-Fi option.
3. Make sure the Wi-Fi is enabled or turned on. Locate and tap Other under Choose a Network.
4. You will be prompted with the Other Network screen that contains the name or SSID of the hidden network as well as Security and Password fields. Tap Security to proceed.
5. The Other Network Security screen will show up next. From the given list, locate and tap the correct security option and then tap the Other Network button.
6. You will then go back to the Other Network screen. Enter the correct Password for the wireless network you are trying to access and then tap the Join button, located at the bottom left portion of the keys.
7. If you’ve keyed in the correct password, then you should now have your iPhone 5 connected to the hidden Wi-Fi network available.
An indicator that you are already connected to the Internet wirelessly is an SSID or name of the hidden network you are in with a check beside it.