After a previous report from Nokia stated that new Symbian devices were coming with Symbian Belle out of the box it was evident that it wouldn't be long before the update was rolled out to all the supported devices. While Nokia did promise to have the update available by February after delayed a Q4 2011 no set date was given by the company until now.
The update would probably be offered through the Nokia Suite instead of an Over The Air (OTA) update due to it's possible large size. You will need to connect your device to your computer using the provided USB cable in order to obtain it.
The Nokia Belle update which will be available for the Nokia C6-01, Nokia C7, Nokia E6, Nokia E7, Nokia X7, Nokia 500 and the Nokia N8 brings a major overhaul to the current Symbian OS and offers features like improved notifications, clean minimalistic layout resizeable widgets and new homescreens.
source - Nokia Vietnam