You have to make prior arrangement with someone specifically, with whom you want to collaborate on a session together. It is not a ‘broadcast’ type tool where you can view/connect to others who are online/live and ready to do a session, just by launching it in an insert slot.
Do you see…?
Maybe try to do some more reading on its use via the website/YouTube videos - they will hopefully explain the basics better than me… 
Good luck.!
Bob