Open YouTube - search for the song/video you need, copy the URL link.
Find a YouTube converter website to convert the audio file to MP3/MP4 format, e.g. https://y2mate.nu/en-rupE/
Paste the song/video URL link into the converter, follow instructions, there’s a convert to MP3/MP4 button to press.
Once converted, download the file.
Go to your PowerPoint presentation.
Click on the slide you want the audio/video to be attached to.
Click on Insert in the top task bar – click on Audio – find download, once found double click and it will be added into the PowerPoint - you can then move/format wherever you want within the slide, e.g. for an audio file, bottom left hand corner out of the way.
Go to Format in the top task bar of your PowerPoint - go to Format options:
Select how you want the audio/video to play, e.g. start playing on click OR automatically, loop the audio for multiple slides OR stop on slide change.
In your PowerPoint document click on File in the top task bar – then click on Import Slides
Find the file you need to copy slides from – open it up
Select slides you want to add by either clicking on the slides or choosing all – Import, selected slides will be added into the point where your cursor is you can then move as needed.