Go to your organisation page (click on the icon in the top-right corner of your organisation page, select the drop-down menu)
Go to the "Settings" tab and then press the "Customize" tab
Here you can edit the functionalities of your organisation page:
When this functionality is active (slide to turn colored), opportunities and events are only visible to members of your organisation. If you make a new activity, you check the box "Member of my organisation" at the requirements option to make a private activity.
Private activities are not visible in the vacancy bank for non-members.