Keep in mind that video on higher tracks overrides lower tracks. You have the main video and audio already in sync. At their left, right-click and LOCK TRACK.
Add the second video above the first. To sync them, the audio waveforms can be helpful. Drag track 2 on the timeline 'til it matches up. You should be hearing them both.
One they're in sync, right-click the 2nd video track and UNlink From Audio. Then, right-click in the area to the left of the track to mute or delete it.
Video from the second track will be seen, except where you have split-out and deleted parts of it to allow the first track to display.
Similarly, the solo can be added on a third track. Its video will override the other tracks.
Drop by again if you need more help.
