Using Facebook to help promote your event is a great way to generate interest and sales for your event.
If you don't have a business account on Facebook or you just want to make a post about your event you can do so by including the event's URL in your post. Facebook will create a preview of your event which will be hyperlinked to your event's purchasing page.
If you have a business account on Facebook you can create an event using that account that will include a direct link to your event's ticketing page. To do that you need to access your business account's timeline and click on the three dots (...) at the top of your timeline and then select the Create Event option.
Under the Tickets option you can paste your event page URL that you're creating the Facebook page for. You can locate and edit your organization subdomain and event URL by following the instructions here. After you add your event's URL customers will be able to click on the Find Tickets option and will be redirected to your event's purchasing page.