Yes you can. I'm not sure in MM2005 can save ogg files if so, choose that one (license free and works great with FPSC). If not, just export/save your music as either a wav or mp3 file and convert it to an ogg file. I'm not sure if FPSC will play mp3 files, I know the sound and story zone objects don't (at least not the ones I've tried).
You could use the wav file, but that will be rather big, so it's better to convert it to an ogg file.
You can import those either through the sound or story zone objects or if you want it as background music, you can set it up in the build level options and choose the music file you've created.
If I do use FPSC to create a FPS? What's a FPS supposed to be anyway???