uricot If you are in the terminal/tty text mode, you can install the desktop environment from the command line directly, by typing these commands:
sudo pacman - S gdm gnome for the Gnome desktop environment,
sudo pacman - S cinnamon gdm for, well, Cinnamon, *or** alternatively
sudo pacman -S sddm kde
You'll be asked to confirm the package installation with a (y)es, and to enter your root password upon pressing enter.
When the installation is done, just type reboot and you should have your chosen desktop