Syncing to computers

I have a family pak .Mac account. I have registered the desktop to transfer data to .Mac. My G4 Ti laptop has a different account name, and is set to receive data from .Mac.

But, the laptop does not show up as a Registered computer on the Desktop computer. Nothing gets synced. How do I register the laptop to use the Desktops account for syncing?

I've tried everything I can think of, and can't find any answers in help or the forum.