Goto the list TAB then press add and select your images. You can use shift and ctrl keys to select multiple images.

See attachement.

Thank you for response. I should have clarified that what I really am looking for is how to get the music to play with sliding of images. I insert the music file, but when slides begin, the music does not play. Can you advise on this

Did you use an mp4 file?

No I used a mp3 file.

Do only mp4 files work as audio?

No sorry i don't think so, Ths sound works only when you start the slideshow and let it run automaticly.

Maybe the files are so nig that the pc gets too busy? I tested with a few small pictures and then the music just plays.

If you check the pictures one by one manually then the music file does not work.