http://www.techieshelp.com/windows-server-2012-install-and-configure-remote-desktop-services/

See also Configure RDS License Server

1. Install Remote Desktop Licensing role
   • Usually, but not always, on DC
2. Control Panel → Administrative Tools → Remote Desktop Services → Remote Desktop License Manager → All Servers
3. Right-click your server name and choose Install Licenses
4. Click Next
5. Select your License Program (i.e. Service Provider License Agreement)
6. Input your License Agreement Number (ours is 8 digits)
7. Product Version will be Windows Server 2012
8. License Type will be RDS User CAL
9. Quantity will be the possible number of users

1. Start Local Group Policy Editor gpedit.msc
2. Computer Configuration\ Administrative Templates\ Windows Components\ Remote Desktop Services\ Remote Desktop Session Host\ Licensing\
3. Use the specified Remote Desktop license servers Enabled
4. Set the Remote Desktop licensing mode Enabled Specify user or device depending on your license