What do you mean you can't download?
When you download and unzip the fie you will get a .nbh file
- make sure you have your phone unlocked -
http://forum.ppcgeeks.com/showthread.php?t=93252
- put the .nbh file on the root of your microSD card
- hold the power and volume down buttons and press and release the reseet button
you should get the rainbow screen and then a message to press power to load the image
- Once the update is complete, press the reset button on your phone
- once you are fully booted to the home screen, remove your microSD card
- go to start > settings > system > wipe device and let the phone reset and reload
you should be good to go!