I don't use OSX I use elementary OS and I installed everything but it says incorrect password and I have no damn clue what the default password is because while installation it didn't ask me for a password!
What documentation or tutorial were you following? The first thing you need to do is create a user (or act as the postgres user on your os) and if the doc or tutorial was an official one, it should be made more clear and you should file a bug, if it wasn't then you should contact the owner and tell them their tutorial isn't clear.