If I am absent in 12th board 2019 and want to give it again as private candidate what is the full procedure to apply and how the exam given?
You can join NIOS.
You can give exam through NIOS. To know about NIOS admission, click on the link
https://school.careers360.com/articles/nios-admission
It conducts admission twice a year. Kindly go through the link to know in details about the admission procedure, fees, exam dates, exam centre and everything.
Thanks