To autosync your voiceover to the entire video, on the story board ( which is the screen below ),
1. Go to Audio -> My uploads -> Either drag/drop or select your file to upload -> Apply to the entire video
2. After applying the voiceover, make sure to select Yes, it does if you have an intro/ outro recorded with your voiceover or No, it does not if you do not have an intro/ outro recorded with your voiceover.
3. In a few seconds, AI will autosync the voiceover with your video. If you wish to further adjust the voiceover sync -> Click on Adjust Voice-Over.
3. Select the scene to wish to adjust, use the green border lines to adjust the voiceover for the scene. Use the Preview icon to listen to the adjusted voice over, hit on Save and Close once done.
*The 'Autosync a Voice-Over to Entire Video' is not available in the Tier 1 or Starter plan.