If you need a tool to unzip the file you can use the free 7-Zip. To install simply unzip the downloaded file and place the package-file/s into the following folder: My Documents\Electronic Arts\The Sims 4\Mods.
If you want them to be naked during other situations you'll have to use nude clothes. Don't worry they wont go to work naked but they'll show all details given by nature e.g. This actually means that you'll get a full nude neighbourhood (female wise). It will replace the EA Standard-Skins (Barbie Skins) or any previous xSIMS skin of all female Sims from teen to elder. This download gives your female Sims a new nude skin.
Only Supporter can download this file! / Nur Supporter können diese Datei donwloaden! WORK IN PROGRESS: This is a work in progress release! So please bare that in mind when posting feedback, which is always very much appreciated.