The system where you enter
Invoke-Command -ComputerName
is a client and the remote systems passed as arguments are servers here.
So you have to execute
Enable-PSRemoting
on the remote systems and not on yours:
You have to run this command only one time on each computer that will receive commands. You do not have to run it on computers that only send commands. Because the configuration starts listeners, it is prudent to run it only where it is needed.