Simply open it and copy Kega Fusion into your Applications folder and it will be ready to use.
After downloading a zip folder will appear on your Desktop. Kega Fusion can be downloaded at this website. Bright Hub cannot tell you where to get roms nor does it endorse the illegal distribution of said roms. Remember, in order to use an emulator one must have legally obtained game roms. Mac users have waited for a long time for a decent Sega emulator and this one does just about everything one could ask for of an emulator. Kega Fusion is the best Sega emulator and it is cross platform, meaning there are versions for both the PC and the Mac.