Well, it's not much different from what you did with your N900, but here's how :

1. You need an SSH client on your computer as on the earlier tutorial. A free SSH client WinSCP is one of the popular softwares for Windows. WinSCP provides both the Remote Terminal access to the N9 as well as the File Transfer GUI. You can download WinSCP from here.
2. Turn on the “Developer Mode” in your Nokia N9 by going through - “Settings > Security > Developer mode” - and turn on the “Developer mode”. You don't have to install other items in Developer Mode and just leave the interface. After turning the Developer mode on you should see two new icons on your home screen “Terminal” and “SDK Connection”.
3. Open “SDK Connection” on home screen and tap “WLAN” to see what’s the IP address, N9 has been assigned on the network. Note this IP address. You don’t need to note any thing else in SDK Connection other than the IP address.
4. On your Computer, run WinSCP. Give the IP address of N9 in “Host name”. User name is “root” and Password is “rootme”
5. That’s it. Click Login to initiate the SSH connection with Nokia N9. – Accept any private key notifications on first time connection.

If the step 4 didn't work, do the following :

- On N9 open terminal and run:

Then on WinSCP ssh in as 'user' (Instead of "root") using the password you just set (instead of "rootme").