Open your profile, the Preferences tab, Notifications. Choose Enable browser notifications and give permission; you do that per device.
You then turn on or off per kind what you want to receive:
- New email
- Invitation to an appointment, calendar reminder, a moved appointment and a reply to your invitation
- A task assigned to you, and a task's deadline
- A project going over its hours budget (at 80 and 100 percent)
- News from your teams