To update Dark Reign with this patch, do the following:

Unzip the zipped file. In it you will find two items: a new .exe file 
and a directory called "deftxt"

At the root of your Dark Reign game directory (default name is "dkreign"),
delete the file "dkreign.exe". Next, go to the file dkreign\dark and 
delete the directory "deftxt"

You can now replace the deleted files. Move the unzipped file "dkreign.exe"
into the root of your game directory ("dkreign"). Then move the unzipped
directory "deftxt" into the directory "dkreign\dark". That's it.