Hi
Sorry don't know much about Ventrilio but I understand you can save the voice sounds from your multiuser game using the "record" button within that software. The resulting file as far as I can gather is a vrf file. If this is correct you should convert this to either a wav or mp3 file, which are formats that can be loaded into VP.
However, going back to your video file. When you load this into VP it should have its associated (linked) sound track display on the Audio track line. If this is correct...does it play OK?
If it does, so far so good.
Get your voice clip onto the media list. (wav or mp3 format preferably) and drag this down to Soundtrack 1 and drop it there.
Irrespective of where it lands,you can drag it left or right with the mouse cursor along the track to the correct position vertically under your video track (and of course the audio track.) It should not jump anywhere else when you release it.
You may have to zoom in or out if this sound clip is a long one (much longer than the video clip) as in timeline mode the video clip is squashed up to enable the sound clip to appear in its entirety.
So if you now have your video clip plus its own audio track (which should check plays OK) and your voice clip is under this on Soundtrack 1 they should play together.
Hope this helps
Nat