Names must match passengers' travel documents. If not, the airline may refuse you to board or charge additional fees.
Identify your first and last name using Machine Readable Zone (MRZ) on your passport. Find it at the bottom section on your passport page, the one with your name, and with a lot of << symbols. Only the leftmost part represents your last name and should be filled in the Last Name column. The remaining part should be filled in the First Name column.