This is a separately ticketed event. If you are in the park during the end of the day, cast members will check you have tickets and gather you into the restaurant (usually) assigned as a waiting area for that year.
Fastpasses are available for you to jump the queues into the haunted houses, if budget allows these are very recommended as the queues especially at weekends can be extremely long.
This really is an adult orientated event, and serious consideration should be given to minors visiting.
The official website is here:
All times are GMT +1. The time now is 10:32 AM.