So follow these steps:
- Download the upgrade package from here: http://d-h.st/JRE
- Move it to /sdcard/ either when plugged into your computer or with a file-manager
- Go to Settings -> About phone -> System Updates
- You will be asked to push the files into the systems memory and the update will begin
The installer package I linked above is a Germany/Austria specific package, I don't know if it will work for other countries too. If you current version in Settings -> About Phone -> System Version is also *falcon_umts.Retail.en.DE it will work for sure. If you have links for other builds, please leave a comment.
Have fun with Android 4.4!