'Coding The Tweet' Proxy Authentication Required


Hi I am new to programming in C# and I wanted to learn about Twitter’s API, so I Googled and found the source code of an application called “Coding The Tweet” which was built using C#. I tweaked it a bit and it worked without a proxy. Can anyone guide me as to what changes I should make to make the application work using a proxy server to access the Internet, with a username and password?