Open OneCare on each of the PCs. There is a link for Your OneCare Circle in the main screen. Any PC that is a hub will show the other computers when you click that link. Any PC that is not a hub will have a link for you to make that PC a hub. You can make any or all of the PCs into Hubs.
For the expired issue:
If your subscription to OneCare shows incorrect or expired in OneCare
- Check your PC date and time.
- Check your subscription status by logging in with your subscription LiveID at http://billing.microsoft.com
- Confirm that this is the same LiveID shown to be the Subscription ID in OneCare - Help/About…
- Open OneCare and click "Check for Updates" to have OneCare check for updated credentials
If your subscription is correctly shown at the Billing site, but incorrect in OneCare and your PC date and time are correct, please contact support.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve