Yes, first of all, you need to create a Whereby account and create a room for yourself. Then you need to configure it in the Fleep conversations where you wish to use the calling integration.
Additionally, the Whereby call needs to be started from Fleep on the web, Windows or Mac version. You cannot create the call from the Fleep mobile apps (Android or iOS), but you can join the call on the mobile apps (Whereby app required on iOS).
More info: Fleep Whereby integration