In winproxy:
Go to File/advanced properties
Click the mapped ports tab
Click new
Port name = Vplaces
Proxy port = 1533
Destination = 198.3.98.70 (excite)
Destination port = 1533
Port type = TCP
Direction = outgoing
Hit OK a few times to get out

In addition repeat the procedure for voice chat ports TCP 3450 and TCP 8000-9000.

In Virtual Places:
Type in a community name
For server address use the IP or name of your proxy server
Hit add Select the new connection and hit Set Default

You will also need to get your web browser to work through the proxy

Since the browser in the Mac version can't be configured this won't work on the Mac