are your contacts already synced to your mac? if so, the 4s should automatically sync to it.
are your contacts synced to exchange? You should be able to export from outlook.
are your contacts not synced to anything? You might be able to find some sort of 3rd party software to extract it into the osx address book but i'm not familiar with any. If not, then you will have to manually do it. I had to when I first went from my dumb phone to iphone 3g years ago.