Install xfce4-systemload-plugin by entering the following commands in the terminal:
sudo apt update sudo apt install xfce4-systemload-plugin
Description:
system load monitor plugin for the Xfce4 panel
This plugins displays the current CPU load, the memory in use, the swap space and the system uptime in the Xfce4 panel.
Homepage: http://goodies.xfce.org/
Version: 1:1.2.1-0ubuntu1
Section: universe/x11