Hi
This should be fairly straightforward...
Place your video clip onto the timeline. (Add File- Select file - Open. Drag and drop file from Media list window onto Video Track1 ...or select it and add it using the drop down menu prompt)
If it has an associated soundtrack that you don't want to play; Mute Audio Track 1 (Loudspeaker Button at left end...It will get a red cross ) Your video clip will now play silently.
Now add your song file to VP in a similar way as you did the video clip. It can be in any common audio format..mp3, wav, etc...) With experience you can even add a second video file and extract its audio,)
Your song file will now found on the Media list under the "Audio Files" tab. (Sound files bin)
Drag the song file from the Media List audio bin and drop onto Audio Track 2 which is the narrow space below Audio Track 1
Adjust it left/right by dragging so it you have it positioned correctly.
Move the red cursor line ("scrubber bar") to the left end of the timeline.Now play the sequence (Click the triangle Play button under the Sequence preview window or press Space)
Your video should now play along with your song on Audio Track 2.
If you haven't muted Audio Track 1 both tracks will play.
Make any adjustments
Save your Project"as" and then Export it to Utube.
You could also, Export it to your PC first, check it plays and then upload it UTube.
Nat