Have you downloaded the Evaluation ISO and want to make it real? Not a problem with Dism.
# Get current edition C:\>Dism.exe /online /Get-CurrentEdition # Get editions that you can upgrade to C:\>Dism.exe /online /Get-TargetEditions # Upgrade to desired edition C:\>Dism.exe /online /Set-Edition:ServerStandard /AcceptEula /ProductKey:C3RCX-M6NRP-6CXC9-TW2F2-4RHYD
The above key is for Server 2016 Standard AVMA activation. You can find more keys for that here if you have Datacenter on your host.