You don't mention if you have any recording software on your computer?
If it's a PC, it's possible to use Sound Recorder to do some basic recording. You can also find some free/share ware sound recording files here
Hitsquad.com - Musicians Web Center
Anyway starting with Sound Recorder.
Start-Programs-Accessories-Entertainment-Sound Recorder..
Try running Sound Recorder, press record and talk into your VOIP mic. Then press stop and playback. Did you get anything? If you did, then you could simply use the VOIP to get started, but it probably won't be very good.
If you didn't get anything, double click on the volume control, then select the 'recording' options and make sure that the microphone option is selected (with most PC sound cards, you can only record from one source at time). Then try again. Make sure that the fader for microphone is turend up as well..
On the other hand you might want to try line in.
Next question is this; Does your amp have a line-out or DI connection?
If so, you'll need a cable that goes from the amp to the stereo mini-jack lead on the line-in connection. On my amp this would be a standard guitar jack on one end and a mini-jack on the other. Some amps have XLR connection, so that is more tricky to describe.
If you are connected to the line-in on your soundcard, you then have to double-click on the volume button again and click on the recording options and then select Line-in as your source. Again, make sure than the fader is half way or higher.
Try sound recorder again....
Hope this helps.. Let us know if you need more info.
Cheers!