Adding voice prompts is an excellent way to guide subjects during an experiment.

Adding sounds to stimulus
Right click on Condition name > Properties > Events and Sounds
Choose an event when you want the sound to play eg: Start of recording, Incorrect Target, Pen is lifted from tablet etc
Then choose either a tone or any audio file in the .WAV format on your computer
Click ok and you're done!

How to make audio clips
Use your favorite audio program to record WAV files or download from the internet
On Windows, the Sound Recorder is a convenient program to do this (Windows XP > Start > Accessories > Entertainment)

Another great resource to generate sample WAV files is here:
The tool allows you to type in some text and download a WAV file that converts the Text to Speech!

Note: AT&T Natural Voices is intellectual property of At&T and any use of their service must comply with their usage policy. Use this information at your own risk.