Hello there,
Indian Army has its own specific department of nurses named as Military Nursing Services (MNS). This exam is conducted once in a year, so you have a single chance to qualify this exam in one year. This is a national level entrance exam and is conducted for 1.5 hours. There are 220 seats in total.
For more information about the same you can check the link given below:
https://medicine.careers360.com/exams/indian-army-bsc-nursing
Hope this information helps you.
Good luck!!