How do you you access the program from a workstation?

This is a silly question, but forgive me as I am not used to web based applications.

I have installed the trial version and am extremely impressed with the product. So much so that we are purchasing it in the next week or so.
My problem is that I have installed the application onto one of my Windows 2003 servers and it runs perfect on the server. If I try and access it from a workstation it gives me the login screen but then comes up with
HTTP Status 400 - Invalid path /homepage was requested
I know nothing about IIS and have never actually published a web page before. I can find no information in the manuals downloaded from the web and would be very very very grateful if anyone could help me out or point me in the right direction.