In this video I will show you how to use Acoustica MP3 Audio Mixer v2.471. This is one of the simplest and most efficient audio editing and recording programs out there. It's free to download as well.
Whether you want to add different audio files together, edit certain ones, sing over recorded music, import entire playlists, this is a great program to test the waters.
http://www.acoustica.com/mp3-audio-mixer/
http://www.pauliojr.com