When you run Contacts for the first time, the Select Address Book window opens.

If you have online accounts configured, they are listed with Local Address Book. Select an item from the list and press Done.

All new contacts you create will be saved to the address book you choose. You are also able to view, edit and delete contacts in other address books.

If you have no online accounts configured, press Online Accounts to begin the setup. If you do not wish to set up online accounts at this time, press Local Address Book.