This is one of the cmdlet that is a little confusing, as the help does not provide exact information. The cmdlet will not take a VM name or vmx file path as input. So how to make changes to the resources for a particular VM?
Get-VM | Where-Object {$_.Name -like “Win7”} | Get-VMResourceConfiguration | Set-VMResourceConfiguration -CpuReservationMhz 25
First Get the VMResourceConfiguration and pass it to the set cmdlet. Here Win7 could be replaced with VM name of your choice. CpuReservationMhz and its value can be replaced with any other resource setting (get-help to find the list).
Prasanna 