Hii Ishika!
You just need to visit the branch ( school ) of the KV sangathan you are interested in, and fill the admission form. The admissions are done as per the merit list after reservation of seats for children of army staff. There are only 2 streams offered, i.e., Commerce a.d science. For science, the average score is 7.6 cgpa and for Commerce, the average marks required are 6.6 cgpa.
Hope this helps.
Good luck!