To run powershell commands on a machine from a remote machine we have to add the remote machine to the trusted hosts list of the host machine.
I am adding machine A
I prefer to work with the PSDrive WSMan:\.
Get TrustedHosts
Get-Item WSMan:\localhost\Client\TrustedHosts
Set TrustedHosts
provide a single, comma-separated, string of computer names
Set-Item WSMan:\localhost\Client\TrustedHosts -Value 'machineA,machineB'
or (dangerous) a wild-card
Set-Item WSMan:\localhost\Client\TrustedHosts -Value '*'
to append to the list, the -Concatenate parameter can be used
Set-Item WSMan:\localhost\Client\TrustedHosts -Value 'machineC' -Concatenate