You have to log in to facebook.
Then you can select "My Events" in menu
On the side "My Events" you will see a list with all the events you are currently planning to attend.
Then you have to hit the "Create Event" button, and then it will take you to a page, where you can fill in all the details about your Event.
This video describes how to creat an event on facebook, but facebook have changed since the video was filmed