When you download Manjaro, there is an edition available that comes with the Cinnamon desktop environment preloaded. But if you've already installed Manjaro Linux and didn't select the Cinnamon desktop when you were downloading it, don't worry, it's easy enough to change your desktop environment in Manjaro.
This is a companion discussion topic for the original entry at https://linuxconfig.org/manjaro-linux-cinnamon-installation