Heya floof. c:
What you need to do, firstly, is to find the music you want to put into your map. It should be (preferably) a .mp3 file, and you should place this individual track into FeralHeart >> Media >> Sounds
When you've done this, go into Map Maker, and in the box where it asks you to put your music file, type in YourSongHere.mp3
Then, test it out (with that little lion you use to run around in your unfinished map). You should be able to hear your music playing.
I hope this helps, floof!
Also, you can edit your posts (without double-posting) by clicking the 'Modify' button at the top right of your post, for future reference.