Hello Aspirant,

First of all you have to apply online for UPSC National Defence Academy & Naval Academy Examination, this is a online process. Form are available on the UPSC site in the month of January and may as this exam is conducted twice in a year. After that you have clear the written test, till now this test is completely offline based. Test are conducted in the month of April and September. This is a merit based exam. Once you have cleared it, you will receive a call letter for SSB interview from service ( army, navy & air force) you have applyed for. Some times call letter don’t arrive so no need to panic you can always download that from your registered email id. SSB is a five day, 2 stage process:- you will be allowed for 2 stage only if you clears 1 stage which is conducted on the 1st day of interview. once you clears the SSB you have to go through a medical examination which will be conducted at the same place where your SSB is conducted. After competition of all the stages UPSC publishes a final merit list of all selected candidates. This merit list is based on the total marks scored by a candidate in his written test and SSB interview.

For detailed information you can refer this article:

https://competition.careers360.com/exams/nda