First, please read: Applying for a U.S. Passport from Outside the United States. Also, do not print applications double sided, one sided only please.
Once you have read the information at the above link and have all the requisite documentation, please book your passport appointment on-line.
If you were born outside the United States and have not been previously documented as a U.S. citizen, and are:
under the age of 18: please see our instructions for obtaining a Consular Report of Birth Abroad.
age 18 or over the age of 18, please review the following checklist (PDF – 96KB). If you are found to have acquired citizenship at birth, it will be documented with a passport.