ohh well 
Tell me you have never used a Linux based desktop before, but you keen to have your Ethernet MAC reandomised as the first step!?
You should start with this guide anaway:
Where the User interface is described - which is a standard XFCE desktop…
In the system tray: the only not mentioned icon is the Network Manager from your sys-net.
(And it is not mentioned because it is not Qubes specific 
after the sound and before the Whonix icons:
If that’s missing, than you have some (fundamental) issue related your sys-net and/or the ethernet/Wifi devices on your machine.