Similarly to discussions, an event can have permissions applied. In Events, you will be able to choose the options of who and how they can access the event. 

Setting permissions when creating a new Event - Firstly create a new event, open the event and hit edit to do so. All access levels available are below:

• All Group Members - you can grant permissions to all Group Members.

• Invitees - Keep as invitees only if you'd like this to be only accessible to people invited to the event.