I wrote a straightforward walk through on Dirrtyclan's forum:
HowTo: Install UT3 WebAdmin
We're running UT3 dedicated server on a Windows 2003 box... Make sure your dedicated install has been patched with version 1.2 or higher (1.3 is currently still beta). Also, grab WebAdmin version 1.3
not the most recent version 1.4 which requires patch 1.3
