Hi
OK. So far you have created a basic video and this will be on Video Track 1 (and possibly on higher tracks if you have overlaid clips) and if it has an associated soundtrack, this will be directly below it on Audio Track 1.
From what you desctibe you also have an audio clip that you wish to play with your edited video. The first step is to add the audio file to VP using the Add File button on the toolbar. It will then appear in the audio clip bin.
At the BOTTOM of the VP interface screen beneath Audio Track 1 you should see an unlabelled track with the text........ "Drag and drop your audio clips here to mix"
If you cannot see this line your preview area need to be reduced in size a bit. So, grab the five small dots beneath the preview screen and pull them up to reduce the height of the preview space. This will then reveal the next unlabelled audio track mentioned above containing the line of text.
Now drag and drop your audio clip from the audio bin to this track which will become labelled Audio Track 2. Move it left/right to the point where you wish it to start playing.
Alternatively put the cursor line at the start of the video, select your audio clip and then click the black down arrow on the Place tab and use the "Overlay on Sequence at Cursor " option at the bottom. This will place your audio onto Audio Track 2 (even if it remains hidden.)
Note that both tracks will play (mix) so if you want to silence one of them you can mute it by clicking the microphone icon at the left end of the track.next to the FX button and ticking the Mute box. (You could also click the microphone icon at the extreme left of the track in question. OR you could also right click the track and select "Mute Audio" from the list.)
Hope this helps.
Nat