1. First, open the main interface of VideoStudio, make sure you are currently in the "Edit" tab, and then click the icon to open the file.

2. Find the video file you want to edit in the Open File dialog box and load it.

3. After the video file is loaded, use the same method to load the background music file to be added.

4. Next, right-click the mouse on the video file, and then click "Insert to" - "Video Track" in the pop-up menu.

5. Then, right-click on the music file, and then click "Insert to" - "Music Track #1" in the pop-up menu.

6. You will see the inserted video and music entries in the track bar at the bottom of the interface.

7. Click the audio icon on the track bar, and then click the play button on the upper right to view the mixed video effect. If you feel that the sound level is not satisfactory, you can increase or decrease the volume of the music appropriately.

8. After the adjustments are correct, you can synthesize the video and audio. Switch to the "***Sharing" tab, and then set the file name and file location.