- First, check to make sure you're running Mac OS X 10.5 ("Leopard") or higher. To check what version of Mac OS X you've got, click the Apple menu and select About This Mac. Only Mac OS X 10.5 or higher support the Yahoo! Address Book sync feature.
- Open your Mac's Address Book application. From the Address Book menu, select Preferences...
- Check "Synchronize with Yahoo!". Click Agree on the terms of service. Then enter your Yahoo! ID and password.
- Open iSync. Click the iSync menu and select Preferences.... Ensure the checkboxes for "Enable syncing on this computer" and "Show status in menu bar" are checked.
- A sync icon will appear in the menu bar (it looks like two arrows in a circle). Click the icon, then click Sync Now.
- For the first sync, you may either merge the data on your computer with Yahoo! Address Book, or replace the contacts on your computer with the data from the Yahoo! Address Book. Choose the option you prefer, then click Sync.
- For subsequent syncs, just click Sync Now from the sync menu.