To record sound, you need to have a microphone, and some software for recording the sound from the microphone.

If you have a laptop, you almost certainly also have a built in microphone. 

If you have a desktop, you probably don't have a built in microphone.  If you have a microphone for anything else, you can see if it will plug into the microphone jack on your computer.  If you don't have a microphone, you can wait until after we meet Saturday the 11th (I have some to share).

If you do have a microphone, but you still can't record sound loud enough that you can hear it, you may need to change some of the settings on your computer:

On a Windows maching, there are settings on your computer that affect the microphone.  In the control panel, if you look under Classic View, you can select "sound'.  the middle tab is "recording".  You should see your microphone there on the recording tab (if not, then the computer doesn't know you have a microphone).  If you click on the microphone you wan to use, it will let you set its "properties", and one of its properties is "levels" which is kind of like a volume control.  I always turn that way up to the highest setting--I figure if I'm too loud the hearer can always turn it down, but if I'm way too soft they won't be able to turn me up enough to do any good.

On a Mac, the microphone options are in the apple menu->System Preferences->Sound.  You can choose the microphone and also the input volume (turn it way up).