How do i begin using my Text-to-Speech device on my phone?
If you mean the new speech-to-text for all input fields, all you have to do is press the microphone key on the virtual keyboard (it's just to the left of the space bar). Talk into the phone, and when it translates it you can see if it is correct. Then hit "send" (or whatever you want to do.
I've been using it for text messaging and for Twitter (via Seesmic app) and - for me - it works like a charm.