Check this option to include audio on the recording.
Select the sound card capturing device on your computer
Record Audio From
Select which recording source you would like to record from. If you are capturing the sound from internet streaming, CDs, sound from player like RealPlayer, Windows Media Player, QuickTime, and what you hear from the speakers. Look for "Stereo Mix, Stereo, Loopback, Wave, Wave Out Mix, Record Master or All".
For sound capturing from the external devices like radio, tapes, CDs, TV, telephone, and etc. Look for "Line-In".
For direct sound capture from mic, look for "Mic".
(Please note that the source name might be varies according to what sound cards you have)
Adjust audio volume for the recording
Audio quality that you wish to use during the recording. Higher frequency, bitrate and channel will generate better quality and bigger file size.