What version Premiere Elements and on what computer operating system?
If you have edited unprotected video on a Premiere Elements Timeline, you can export it to a file in a format consistent with your needs. The Elements Organizer File Menu/Get Photos and Video/From Files and Folder offers a wide choice of Elements Organizer supported formats for import into it. Some related to import into the Elements Organizer and some as it relates to the Elements Organizer Slideshow. The later usual work if the video is wmv/Windows Media compatible.
It might be toward your advantage to create the Elements Organizer Slideshow without the video, output the finished Elements Organizer Slideshow to Premiere Elements, use the Break Apart Elements Organizer Slideshow command on the slideshow in Premiere Elements, and then add your video.
But, please look into any protection issue as it relates to your source. My last recollection was that the YouTube Agreement did not allow for downloads of it videos unless they were you own or you had special permission.
We can move forward with further information for unprotected video based on the details that you present.