1)- Get your Snes Emulator of choice (I use ZSNES)
2)- Find a working ROM of this game, posting links is illegal so you have to do that on your own, just google it, should be pretty easy.
3)- Place the ROM in the same file folder as your emulator, boot it up, and it should be accessible through the menus.
4)- This is optional, but if you want an English translation, go to http://serenesforest.net/general/patch.html and download the FE4 translation patch, and click on the link "general patching instructions" if you don't know how to patch files.
As far as I know all of this can be found on a mac.