Install the kde5 package, and optionally, the kde5-baseapps package.

To use the "Networks" widget, enable the dbus and NetworkManager services.

Installing the kde5 package also installs the sddm package, which provides the sddm service for the Simple Desktop Display Manager; test the service before enabling it. If you are not intending to run SDDM via a remote X server, you will need to install either the xorg-minimal package or the xorg package. By default, SDDM will start an Xorg-based Plasma session, but you can request a Wayland-based Plasma session instead.

If you wish to start an Xorg-based session from the console, use startx to run startplasma-x11. For a Wayland-based session, run startplasma-wayland directly.