Every notification that's been sent to you is saved inside your personal notification center. In case a notification was sent, but you haven't read it yet, you'll see a red sign on the bell icon. To access notifications on the desktop, simply click the bell icon at the top right corner of the virtual event screen:
To access notifications in the mobile app, follow these steps:
Tap on your icon at the top left corner when you are on the main page fo the app or the menu button when you are in a particular event.
Tap on the "bell" button near your profile pic and view the notifications.
If you are an event organizer, check this article for the info on how to send notifications.