my minor son is attaining 18 how to renew the passport and when

My son is below 18 in november he will be 18, therefore his passport will expire, how should I get his passport renewed since he is becoming adult and what is the right time to apply

He should apply after attaining 18 yrs of age with fresh set of documents of his address proof like Adhar card, bank passbook etc and education certificates

He will be issued 10 yr valid passport after completion of procedures