Hi David,
Windows Firewall is your computer's built-in defense against a possible malware attack. Only allow apps that you trust to communicate through your firewall. To add an exception, you must be logged in as administrator. With that said, assuming you are logged in as administrator, what is the error message that you are getting?
In case you need a refresher, here's how you can add an exception. Go to Control Panel> View by: Small icons > Windows Firewall > Allow an app or feature through Windows Firewall > Change settings > Allow another app> Navigation to the location of the app> OK > Add. Restart your device afterwards.
We look forward to your response.