Using the SETTINGS tab under My Fleets, you are able to define whether you want to add notifications regarding a vessel when adding her to a fleet of yours (or delete notifications when removing her from a fleet). In case you have never defined a default selection regarding this matter, you will be asked to choose accordingly.
There you will be able to find your Notification Preferences, so as to automatically create vessel notifications.
Additionally, you can change your preference per case, when adding or deleting vessels, without affecting the above settings. If you marked the option “Create vessel based Notifications”, a group of notifications will be created each time you add a new vessel to an existing fleet of yours.