Hi albehany, for installing the Voronoi script there are some instructions on how to install plug-in commands in the FAQ here:
http://moi3d.com/faq#Q:_How_do_I_install_a_plug-in_script.3F

The CustomUI and node editor have a lot more stuff in them than just one command though, so they are a little different.

For CustomUI first make sure you're getting the latest version which you can download from Max's page here:
http://moi.maxsm.net/media/files/

Find the one there named CustomUI.1.03.win.mac.zip to make sure you have the latest.

Then unzip it and copy the unzipped files into the directory where MoI.exe is at - to find it follow the same instructions in the FAQ above, but instead of going all the way down to drive_c/moi/commands, go to drive_c/moi . One file will be overwritten in the ui sub-folder which you want to allow.


For the nodes editor, I think the most recent release is here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=7713.76

and the installation instructions are here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=7713.34

To find the "ui" directory that's mentioned there, again follow the same instructions in the FAQ but instead of going into drive_c/moi/commands, go to drive_c/moi/ui .

Hope that helps!

- Michael