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Installing Plank Themes

There are a number of themes available for Plank. In order to use them, you have to first install them.

To do so, open up "Files" and open the folder /usr/share/plank/themes.

Now, copy the folder of the theme you've downloaded, and paste it into /usr/share/plank/themes. (You should see 2 files in this folder named dock.theme and hover.theme.)
That's it.

Open up the System Settings from your applications menu and select Desktop → Dock. From here, click on Theme and you should see the theme(s), you've just installed.

To apply it, simply click on it, and you're done.