CiviCRM integration with Eventbrite
You will need to create extension to have Eventbrite sync with CiviEvents. Here is some guideline on how to approach this


Create extension.
Add page using civix
In run() use CiviCRM api to create entries in civicrm table.


Reference : 

Mandrill extension uses same approach i.e to create entries in various civicrm table upon webhook call. This might find you helpful to develop your extension
https://github.com/JMAConsulting/biz.jmaconsulting.mte/blob/master/CRM/Mte/Page/callback.php