Using iTunes you can convert the audio to MP3, which will work in Premiere Elements.
Unless it's copy protected, as many iTunes songs are. (Which is why I buy my music from Amazon.)
To get around copy protection you need to burn your iTunes songs as a CD and then use Windows Media Player to rip the music back to your hard drive as an MP3.
For best results, in fact, download the free program Audacity and use it to convert the MP3s to WAV files, the ideal audio format for Premiere Elements.
iTunes has been relaxing things a bit lately -- but it used to take a remarkably convoluted system to make their music usable in a video project!