This article explains how to export and import your address book using the contacts application in Mac OSX.
Export your Address Book
Click [File] > [Export] > [Export vCard].
Choose a location to save the file.
You have successfully exported your contacts from Apple Contacts.
Import your Address Book
Click [File] > [Import].
Locate the file containing your contacts.
Follow the prompt to complete the Import process or review any duplicate contacts.
You have successfully imported your contacts to Apple Contacts.