Dial *#0000# and under Options check for availability.. If available go for it. You may also try thru' Nokia Suite (Go to Tools-->Software Updates) and if available follow instructions CAREFULLY. Last chance is to try thru' Nokia Software Updater.
If there is NO update available thru' any of these 3 methods, yo may try your luck at Nokia Care. Else, you can not do it and will have to wait till one is made available for your Device.