Yes, you do need a microphone to record your voice. Just follow these simple steps:
~ Click "Record" button, the record dialog will be displayed.
~ In the record dialog, select microphone as the audio input channel by selecting "Microphone" in the second pull down list on the left
~ Plug your microphone in now and speak. You should see the VU meter on the right moving as you talk.
You can also record from other sources (such as CD Player, phone, line in, etc..) by selecting different audio input channels.