Please note, Wi-Fi proxy settings should be entered whilst connected via Wi-Fi only. Ethernet proxy settings may be entered at any time.
Open Settings and select Wi-Fi.
Press and hold on your preferred network and select Modify network.
Scroll down to Advanced options and check the box.
When it appears, tap the Proxy drop down menu.
Enter your proxy settings and tap Save.
Open Settings and select Ethernet, and then Proxy.
Enter your proxy settings and tap Connect.