The first thing you need to do is fill out a DS-11 form, which is the application for a us passport. Make sure you do NOT sign the form until the acceptance agent tells you too.
You will need at least one of the following as evidence of US citizenship:
[Previously issued us passport]
[Birth Certificate]
[Naturalization Certificate]
[Certificate of Citizenship]
You will need your social security card as well as one of the following as proof of identification:
[Previous Passport]
[Naturalization Certificate]
[Valid Drivers License]
[Government ID]
[Military ID]
You will need to photocopy all of the identification documents and proof of citizenship that you bring. Ensure the front and back are copied.
You will need to provide two passport photos. Do not use photographs of you wearing a hat or sunglasses. If you use prescription glasses, hearing devices or anything else that you wear everyday, wear it for the picture. The photo should be no more than 6 months old and two inches by two inches in size taken with a white or off white background.