you can go thru the Forex example provided by SDK .The SDK has documentation for CiscoURLProxy where u have to make a JavaScript instance of passing IP addr or server name of your proxy server ,then using the same instance pass the userID & password to it seperately .How to pass all this is there in documentation.
I have modified one such application which reads NEWS headlines from a website & the internet was accessed thru squid proxy.
-Sandeep Nag