Hi mario, there are some instructions for how to install plug-ins on the FAQ answer list here:
http://moi3d.com/faq#Q:_How_do_I_install_a_plug-in_script.3F

Make sure you've unzipped the files, you don't want to copy the .zip file itself directly into the commands folder, you need to unzip it and then install the files which were contained in there.

If you are still having problems maybe you could show a screenshot of what your keyboard shortcut and commands folder looks like.

- Michael