lol, yup, you created a nandroid already, so you should be fine there.
Do you have Fresh1.1 downloaded to your computer? If so, don't unzip it, just copy it to your SD card of your phone. If not, download it
Now, unmount the card, and turn the phone off. Turn it back on while holding the Home button down until the HTC logo comes on. It should go into that black screen with green text.
Now scroll down to the "Apply SD card: Choose zip", and select that. Then select the Fresh 1.1 file you put on your SD card, it should be the only thing to show up.
Run it (press home to confirm), and it'll go through a process. When it finishes, select "reboot now".
It'll likely take a little while the first time it boots, but you should now be running Fresh 1.1 (it'll be very obvious while it's booting if it worked, cuz it'll say "Freshhhh" to you lol)