You may only use the Windows templates for evaluation purposes.
Installing a license
Open a command line with administrative privileges (cmd or powershell)
Execute the following:
DISM /online /Set-Edition:ServerStandard /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEula
Where 'ServerStandard' is replace with your Edition and the XXXXX is replaced with a valid license key.
Generally our templates are for retail channel only. But it is possible that volume licencing method will work with no guarantee.