In Windows Server 2012, remote management is enabled by default but not Remote Desktop. To enable RDP on the server, add the target server to the Server Manager and run remote Powershell console.

On the remote Powershell console, enable remote desktop and firewall using the following cmdlets:
1) Enable Remote Desktop

set-ItemProperty -Path 'HKLM:\System\CurrentControlSet\Control\Terminal Server'-name "fDenyTSConnections" -Value 0

2) Allow incoming RDP on firewall

Enable-NetFirewallRule -DisplayGroup "Remote Desktop"

3) Enable secure RDP authentication

set-ItemProperty -Path 'HKLM:\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp' -name "UserAuthentication" -Value 1