Open the download, and you're going to place the various files inside into their appropriate spots in your FeralHeart folder.
Looking at the last three letters of a file's name, you may see some of these files, and they go in the spot specified--
.fhm, .fho, .fhs, and .fhw files go into FeralHeart>>Exports (Most files go into Exports, as Brittnie said.)
Any music/mp3 files go into FeralHeart>>Media>>Sounds
Restart FH, and you should be set.
Of course, your map may not have all of these files within it, but this is the gist of a map. Also check inside the download to see if the map maker put a "ReadMe" note pad with further instructions for installing the map.
I hope this helps ya!