Renewal of US Passport for Minor in India

Hi All,
My 5 yrs old son who is US born, his passport is getting expired in June 2021. We are curently in India. I want to renew his US passport. Can someone advise me the process of renewing his US passsport while in India.
I filled the DS -11 form. I have all the other documents ready with me. Is the next step to book an appointment? I do not see any open date to take appointment. Can it be renewed without Appoinment at consular office?