If your device is new or has been reset:
If your device is already activated:
Alternatively, if your device is currently activated and connected to a Wi-Fi network you can access the Proxy settings by tapping Wi-Fi at the top of the Network connection screen, and then tapping the gear icon next to the selected network.
Choose Manual from the Proxy options. Enter the Proxy Host IP address/FQDN and the Proxy Port number.
If you want to use Digest authentication:
When you are finished, tap the checkmark on the top right of the screen.