If the computer has a built in microphone, you could test it first by trying to
capture a YouTube video.
If it doesn't have a microphone, you could
A. Buy a
splitter for the audio out.
1. Send one of the outputs to the speakers (assuming external speakers) use a male at both ends cord from the other output at a splitter to the microphone in jack.
B. Buy a
USB microphone (preferable) or a traditional one to plug into the microphone jack.
Again, test it before that day in case you need to adjust the microphone sensativity (within Camtasia).