You can download Betternet on your iOS device here.
After downloading the app, you need to launch it and then simply tap on "connect" button. Then, you need to install a profile and it asks for a 4 digit passcode which is the one you enter to unlock your device. Please note that you need to have internet connection on your device. Also make sure that the ISP you are connected to has not blocked VPN connection.
Second: Wait until the app connects
Third: Enjoy surfing anonymalously when the app connects