Log into the web browser admin
Go to Settings, then click on Edit Settings
Change Connect Type to
WinINetProxy
In the address and port fields, put the other queue you want to go through
Change any other settings you want there

Click Submit at the bottom.
To get it to get any WUs, you will need to first send a completed WU through the queue. For the first time a UserID connects, it will trigger a passthrough operation, which will connect to the Seti Server (or another SetiQueue, if specified in the Proxy field in the settings) and download some WUs
Any more questions, just ask
Garry