How to configure proxy in mobile operating system?

Android 4.0
  1. Open the menu then go to Settings.
  2. Go to Wireless & networks.
  3. Go to Mobile networks, then VPN Settings.
  4. Select Add VPN then select PPTP VPN.
  5. Enter the VPN name then OK.
  6. Go to Set VPN server, enter the IP address of Hostname of the VPN server then OK.
  7. Turn on the Enable Encryption.
  8. Go back to the VPN screen and select the VPN you setup just now.
  9. Enter the Usernamestrong and Password then Connect.
How to configure proxy in mobile operating system?