To use the Text-to-Speech (or the Speech) on your Nokia device, select Menu > Messaging > Inbox, highlight a message and select Options > Listen.You can open the Speech menu in device settings to choose different languages, voices, speed, volume etc. (For Example on the Nokia E52, select Menu > Ctrl. panel > Phone > Speech)
To download languages open the Speech and select Options > Download languages. The internet connection is needed to download the additional languages.