I have added the packages netload and systemload for XFCE and both are supposed to go in the panel. See here:
Netload [Xfce Goodies]
Systemload [Xfce Goodies]

The usage section states: "Just place it into your panel" However, there may be some settings required to be able to see the plugins at work. How is this achieved? Thanks in advance

EDIT: right click on the panel, select Add items and select the aforementioned plugins.