To add a new subscription, first click in the last field of the list. Next, select or enter the Windows Installer events that you want this control to subscribe to. Finally, in the Attribute column select which of the control's properties will be set by the event.

For example, suppose you wanted to increment a progress bar to indicate when all of the files had been transferred. In that case, you would subscribe to the InstallFiles event and have it set the Progress property.