Hi,
For how to Secure Remote Desktop Connection with TLS 1.2 ,you can refer to the method in the following link:
https://social.technet.microsoft.com/Forums/en-US/ff98d296-42cb-4f4d-a69f-c8dea82453ad/how-windows-server-2012-r2-use-tls-12-for-remote-desktop-connection?forum=winserver8gen
Best Regards,