This might sound a little intimidation but is actually painless.
1. Download (and install) the latest BlackBerry Desktop Manager Software:
http://na.blackberry.com/eng/services/desktop/
2. Download the latest device OS (save to your desktop):
https://www.blackberry.com/hhupgrade/
3. Close Desktop Manager, if it’s open, and launch the download from #2 above.
4. Connect your Phone with the USB cable.
5. After that installer runs, it should open Desktop Manager and you will see a button “update now”.
Installation time: (about 30-50 minutes).
**Not responsible for your data.
If your device gets “nuked”, this is a great link:
http://crackberry.com/blackberry-101-lecture-12-how-reload-operating-system-nuked-blackberry