First name: enter all your first name according to the passport.
Surname: enter all surnames according to the passport. You cannot abbreviate your names or enter them as initials only.
If you are getting married, you must book your trip in the same name that you will have in your passport when you travel.
If several passengers have identical first and last names (e.g. father and son), then a second first name must also be entered to distinguish them both.