When right-clicking on a station icon on a map display or on a station callsign in a tabular view, if the callsign appears to be a normal ITU-standard amateur radio callsign (uppercase ASCII letters and digits, some of both letters and digits, not ending with a digit), the Show Licensee Info option will be available on the popup menu. If this menu choice is clicked, it will search all callsign info previously downloaded by the Load FCC License Database and Load RAC License Database menu choices for a matching callsign. If the callsign can be found, a popup window with the licensee's registration information will be displayed. If the licensee cannot be found in the current database contents, an error message will be displayed.
The main menu bar's Query menu also has a Show Licensee Info menu choice that will pop up a dialog to ask for the callsign to lookup, and will thwn try to find the callsign's information in the available databases.
Note that the only license databases currently supported are the American, Australian, and Canadian databases, so callsigns issued by other countries will not be found unless you have an account with QRZ.COM and the callsign you are looking for was registered there.
Note also that this uses a locally-cached copy of the license databases and any QRZ.COM queries previously made, so these lookups can be performed when YAAC is disconnected from the Internet, as long as the databases were loaded from the Internet prior to disconnection.