When you are on your page, the menu "your events" allows you to see the list of your current events, if you have bought an advertising spot for your page, you can schedule the highlighting of your event thanks to the "schedule" button on the right of the screen. 

A calendar corresponding to the weeks of advertising you have paid for will appear. 

You can then choose which days and in which departments you want to promote your event. 

On mobile, you must first go to your page, then to the event tab. Then go to the settings on the top right and click on "Planning". Your event will then appear, click on "Promote" to put it on display.  

You can then choose the event you want to promote. 

Web version :

Mobile version :