. Open "Insert" -> "Sound" -> "Sound from File" and insert the prepared sound file (MP3 or WAV, etc., assuming that "Dawn of Heroes.mp3" is now inserted );

2. At this time, the system will pop up a dialog box asking "How do you want to start playing the sound when the slide is playing?" Click "Auto" to play the sound when the slide is displayed. There is a "speaker" icon on the film

3. Click to select the "speaker" icon and select "Animation" -> "Custom Animation";

4. Click on the right side of the window In the "Custom Animation" dialog box, drop down the arrow on the right side of "Dawn of Heroes.mp3", select "Start from previous item", and then click "Effect Options";

5. In "Effect Options" "Settings page, the default option of "Stop Playing" is [When clicked]. According to your needs, if you want the background music to exist in "X" slides, select "On X" in the "Stop Playing" option. Slide After”, where X represents the number of slides you want the background music to persist. If you want to add full background music, just insert the music file on the first slide and change the "X" after the "Stop Playing" option to the total number of slides. Or you can fill in a very large number as long as it is larger than the number of slides you have.