During addition any new person in your master passenger list or editing already added passenger. you'll get option to add AADHAR NO., if name & birthdate will match the aadhar data then it'll be verified. If it's not, then first verify entered information matching with aadhar information , then remove it and update it again.
after 12 tickets (previously 6) you would need any one passenger with aadhar verified to book tickets. it's simple.
and it won't affect already booked ticket.