Press on the profile icon at the top-right of your screen
Go to your organization 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 "Customise" tab
Here you'll be able to edit the functionalities of your organisation:
When this functionality is active (the slide button is colored), you can select opportunities that you wish to show on the homepage of your organisation page and in the opportunity section of your organisation.