In Windows launch regedit:

Browse to subkey HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TerminalServer\WinStations\RDP-Tcp\ 

Right click PortNumber and click Modify 

Once the Edit window shows up switch the Base to Decimal and enter the Port you want to use under “Value data:” and click OK 

Restart the server

In the Google Cloud console go to the Network --> Firewall rules section 

Add a new rule and give it any name following the google naming convention

The Source IP can be 0.0.0.0/0 for all or you can specify what IP’s to use as a source

Fill in the port number you want to use (please note this needs to be the same port number used in the registry change made on the server)

Create a tag for it, this can be anything you want it to say as long as it follows the google naming convention. We recommend the same as the firewall rule name to make it easy to remember

Click “Create”   

Go to the Compute Engine/VM instances section of the Google Cloud Console

Select the VM instance you want to apply the firewall rule to

Once inside of the VM Instance page on the Google Cloud Console click on EDIT

Under Tags add the same tag you created for the firewall rule, in the example below obscure-rdp-port and scroll all the way to the bottom of the page and click Save 

After following these steps you should now be able to RDP into a server using the new port assigned to RDP.