ScoreHero is a Guitar Hero modding community that makes custom songs just like our community. The only difference is the way they package their custom songs. Frets On Fire needs a few extra files than are usually provided with ScoreHero community-made songs. Scorehero charts will usually only come with the notes.mid or a *.chart file. If one comes with any extra files, chances are they won't be needed for FoF.
To "convert" it from ScoreHero to FoF format, it also needs a guitar.ogg file, a song.ini file, and optionally a song.ogg file. To go about converting it, you would need to have an mp3 of the song. You would then convert that mp3 to ogg format and save it as guitar.ogg. If the song comes with the notes.mid file, you're work is done. You would then create a song.ini file for the song, bundle them all in a folder, and put in your data/songs folder. If it comes with a *.chart file, import the chart into GHEx and then export it as notes.mid.
Congratulations, you just converted a ScoreHero song. If you submit it to the FoF Fan Forums, always remember to give the original ScoreHero fretter credit.