To use Wi-Fi on your phone, you need to access a wireless access point or 'hotspot'. Some access points are open and you can simply connect to them. Others are hidden or use security features, you must configure your phone to be able to connect to them.
Turn off Wi-Fi when you're not using it to extend the life of your battery.
If you're out of the Wi-Fi zone or have set Wi-Fi to off, additional charges may be applied by your mobile service provider for mobile data use.