Lubuntu 15.10 Latest Cinnamon desktop Installation
How to Install Latest Cinnamon 3+ desktop on Lubuntu 15.10 Wily Werewolf i386/amd64 GNU+Linux.
The Cinnamon Nightly Lubuntu Apt Repo PPA is not stable and so the desktop may manifest some sort of Misbehavior.
The Cinnamon desktop is an environment based on GTK+ 3. The project originally started as a fork of the GNOME Shell, i.e. a mere graphical shell. Cinnamon was initially developed by (and for) the Linux distribution Linux Mint.
Cinnamon is a desktop environment which combines a traditional desktop layout with modern graphical effects.
Now with Cinnamon 2.x it has become a Complete desktop Environment and not merely a frontend for GNOME like GNOME Shell and Unity.

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Open a Shell Terminal emulator window
Ctrl+Alt+t on desktop
(Press “Enter” to Execute Commands) -
How to Enable the Latest Cinnamon Apt PPA for Lubuntu
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Installing the Cinnamon desktop for Lubuntu 14.04+.
sudo apt-get install cinnamon
If Got “User is Not in Sudoers file” then see: How to Enable sudo
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Then after Log-Out you’ll be able to Switch on Log-In Screen to Cinnamon.