Don't get scared. If you know how to to basic work in the CK, then it's not that hard.

1st
You need a music track. It needs to be
.wav
bitrate: 16 bits
mono
I'm not sure if length is an issue. The longest I've used is 9min 41sec
All songs need to be in: Skyrim > Data > Music

2nd
In the CK, find the <Audio> tab, then <music track>. Right click and "create new." Name it something you'll remember, browse the music folder(of your pc) for your song. In the drop down is "Single Track" select that.

3rd
Under the <Music> tab, find "Music Type." Create a new type and name it accordingly. Then add the songs you want into the list.

4th
In the cell, use the Music Type drop down to select your music type. Save. Set the priority to high.

Note: Sometimes the music will not play. This is normal as far as I can tell. Sometimes just leaving the cell and coming back will cause the music to play.

For changing the music from Mp3 to WAV I use this site: http://www.online-convert.com/