Start by enabling the extra questions
Click on Manage --> Booking Engine --> Extra Questions
Click New Question
Click Enable on the question Event Type
How do I create my own event types?
Go to Manage --> Business Settings --> Leads
In the Event Type box, write your event types, one per line
Where do I find the event type on the bookings?
Go to the overview of the booking by clicking on Sales --> Bookings
Scroll down to the lower right corner and click Edit
The event type is listed in the Additional Info section of the booking
You cannot enter the event type when creating a booking manually; you will be taken to the overview once the booking is created.