How to install a new MU.LAB skin:

* Download the zip file and extract it to a new folder.

* Move this new folder into your Mulab/App/Graphics subfolder.

* Now make sure that when you go into that new folder ("Loox....") that you see subfolders like Common, MultiSampla, MuSynth, ...
  If not, there may be another intermediate subfolder ("Loox....") due to the unzipping.
  In such case, move all of the content of that extra subfolder one folder level up.

* Now in MU.LAB -> Edit menu -> Choose Skin, the new skin should be available.