What do you mean by "on my iTunes"? If your music files are in the iTunes folder on your PC, then connect your Android device via USB (turn on USB storage) and then copy your music files into your "Music" folder on your Android device. Once the music files are in your "Music" folder, PowerAmp will discover them.
If your music files are only on an iPod/iTouch, you'll need to get them onto a PC (perhaps by syncing to iTunes on the PC) and then transfer them to your Android device as described above.