open putty
enter the remote hostname or ip address
enter the ssh port of the server
I'm using a private key to connect to the server , I will add the key
select tunnels
In source port enter any unused port for your local port
enter the local address of the computer you want to connect and the remote desktop port
click on add
click on open
now the ssh tunnel is active
open remote desktop and type localhost
3390
click on connect