If you have already published an event on Billetto, simply copy the event link and paste it into the "Tickets" section in the Facebook event creation page, like so:
Please note that you can only add ticket link to Public Events on Facebook, if you don't see the "Tickets" option in the form, you probably need to make your event "Public" (top-left drop-down).
If you have already created a Facebook event, you can add a link to the tickets by clicking "Edit" under your Facebook event picture and inserting the link in the same way as above.
Need help creating your Facebook event? We have a handy video tutorial over here: