To enable Remote Desktop Services (RDP) you might need to either use Group Policies or by physical access on the computer or server. Remotely you would need to use command line with PSTools which can be downloaded here.

Once downloaded and extracted type in the below

psexec.exe \\ reg add “HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server” /v fDenyTSConnections /t REG_DWORD /d 0 /f

psexec.exe \\ netsh firewall set service RemoteDesktop enable