Request a passport application form from Direct.gov.uk or complete the application online. Some post offices have Passport Check and Send services where you can pick up your application immediately.
Complete the application form and sign it. If applying online, submit it and wait. Identity and Passport Service will print it on their end and send it in the post for you to sign.
You will be required to provide your birth certificate and U.K. national identity card to prove your British citizenship to Identity and Passport Service. Alternatively, provide your Certificate of Naturalisation. These must be original documents, not copies.
Send your completed, signed application and supporting documents along with the application fee to the following address:
Identity and Passport Service
Globe House
89 Eccleston Square
London
SW1V 1PN
Copy down your application's barcode. This allows you to track its progress. If you have any questions about your application, you will need to reference this number.