Go to Settings.
In Wireless and networks, click on Wi-Fi
On Wi-Fi, click the router you want to use to connect to the internet.
Click on Advanced options>Proxy>Manual
Type the Proxy on the Proxy hostname field and Port number on Proxy port
Click Connect, then OK to save settings.
Next, open a browser to ip-check.net to verify that the IP displayed is the proxy's IP address.
If so, you have successfully proxied your internet connection.