Subtitles on Sony Vegas?

I'm new to Sony Vegas 9. How do you add a subtitle or title to the video while its playing?

While they may sound similar, subtitles and regular titles are two completely different things.
To add a title, create a new video track ON TOP of your existing video, click the Media Generators tab, then click Text and drag the Default Text icon down to track 1.
Adjust font size, placement, colour, etc. as desired.

Mike