You can only do this if you're a PerformanceGuard administrator. Ports contacted by the computers that have PerformanceGuard agents installed are automatically discovered by PerformanceGuard and saved in the backend database. By selecting ADMINISTRATION > Port > Port List you can select which ports to monitor by adding them to the monitored port list. It's possible to manually add new entries from the discovered ports list to the monitored ports list.
Monitored
Remove from monitored: Remove the selected ports from the monitored list.