Every event can have its own reminder. While you are creating or editing an event, just switch to the Reminder tab in the left menu. Turn on whichever of the three channels you like, and set the timing to suit you. Here is how it works, step by step.
Reminders
Channels and default timing for event reminders.
Desktop reminders
Reminders arrive on this device as a notification even when the tab is closed.
If you turn this channel off, no reminders will be sent through it even when enabled on individual events.
Reminders
Channels and default timing for event reminders.
These values are used as defaults when you add a new reminder; you can change them per event.
Timed Events
Default reminder timing for events with a specific time
All-Day Events
Default reminder time for all-day events