If you download the zip of the files, then extract the files to a folder you'll find some folders called cohokum and common.
If you then go to the folder that you have EECH installed into, you also find folders called cohokum and common. So copy the files from the folder in the zip file into the same folders in your game install, and it should replace them. You might want to take a copy of the original folders before you copy over them.
I hope that's some help.