reg add "HKLM\system\currentcontrolset\control\terminal server" /v fDenyTSConnections /t REG_DWORD /d 0
... at command prompt.
If you want to enable RDP on remote machine, start
reg add "\\hostname\HKLM\system\currentcontrolset\control\terminal server" /v fDenyTSConnections /t REG_DWORD /d 0
... at command prompt.