install the application on your PC, boot up Desktop Manager and connect your BlackBerry - you'll be prompted to install the update.
If you're going to install one networks firmware on another networks BlackBerry then you must perform one additional step before you boot up Desktop Manager and connect your BlackBerry. After installing the firmware on your PC go to......
C:\Program Files\Common Files\Research In Motion\AppLoader
.....and delete the vendor.xml file. You will now be able to install it on you T-Mo device!!!