Hello jcho, Welcome to the forums.
I took a look at the Iomega user documentation for this - it is dreadful. No help at all on the media side.
Anyway, your report says that the box is running a version of TwonkyMedia which is a UPnP server that can stream music to your SoundBridge. This program normally needs some configuration, although it is possible that Iomega have a version installed which is very restricted. When TwonkyMedia is running on a PC or Linux platform, the usual way to configure it is using a web browser. The way to do this is to tell your browser to go to the IP address of the Iomega box and to talk using the correct port. TwonkyMedia usually uses port 9000.
So, if the IP address of the Iomega box on your network is something like 192.168.1.35 (just an example), then you would tell your web browser to go to http://192.168.1.35:9000
This would give you some options including some configuration options. You may then be able to set up which folders are shared.
Please try this and let us know how you get on.