As @seumo said nearest samsung store. I reccomed it as you will always get that premium LCD screen rather than a cheaper one that is more likely to break again. Otherwise if the crack isn't that bad I suggest you just keep the phone. Chuck a R60 screen protector on it, you can do this if you need to save up for a replacement or if it doesn't affect you indefinatly. Keep in mind also that if you get it repaired at a non samsung store your device will become uncertified and won't be eligible for certain things.
