Above your board is an icon named 'Show Observers'
Click this icon and the list of observers should show below your board.
If you do not have your board console open then the list appeared in the Main tab of your Channels Console.
To open/close your board console click on the 'Toggle Kibitz Window' icon above your board.
Or use the command 'allobservers' combined with username or boardnumber.
Example type on the command line of your board or console: allobservers Eendje
You can also use the shortcut 'allob'. Example: allob 242
For more information read "help allobservers".