DarwinPorts and Proxy

I've just installed DarwinPorts on Tiger. I'm behind my University
proxies and I can't get this to work for the life of me. Now, I swear
I had it working once.. and I *know* Fink can work.. I was just
wondering if someone can help me out by telling me exactly what to do
in order to get this working.

my proxy url: http://172.16.250.1:8080

As this is an authenticating proxy, I do have a username and password
to go with that.. but I'm obviously not going to say those there, so
just do user:pass..

Thanks for taking the time to read this!

Steff!