Right-click on the audio clip in your timeline and select "Detach Audio".
Drag the detached audio clip below the video clip in your timeline.
Click on the audio clip and drag it so it starts at the same time as the video you would like it to begin at.
Additionally, ensure your audio source file and your video project have matching frame rates and resolutions to facilitate smooth synchronization. For best results, convert both of them to have matching properties beforehand.