You will have to wait for TIM to approve the update. When nokia makes new firmware the networks have to test and approve it before nokia is allowed to release it for that networks customers.
Unfortunately many networks are slow to approve new firmware as they don't consider it to be a priority. Some networks don't approve any new firmware at all leaving customers stuck with old versions forever.
So all you can do is be patient and hope that TIM decide to release this version to it's customers.
If TIM has a customer forum you should post on there asking when they intend to allow the update.