The theme was basicly inspired by Plank's default theme and the slightly transperant "Pantheon theme" by Cassidy James [link]
- Extract the file, open the folder created after the extraction and copy and paste the folder "theme" in ~/.config/plank/ replacing the existing files (this will overwrite the default theme, so back it up if want to use it again at some point).
- Plank should immediately reflect the changes. If not, restart it.
P.S. The two .png files are just previews