you first need to activate the mod
I agree the readme could be better.
start the nehrim launcher(not the exe on your desktop, look in the file for the launcher) , go to data, unselect everything(also Oblivion.esm!!). after that, select the 3 nehrim files.
then it should work.
Also I had the "purple texture issue"(this means the oblivion engine can't find it's textures) easily solved by copying the textures file from stock oblivion into the nehrim folder