Hello aspirant,
Indian statistical institute is a college where two undergraduate courses are taught. It is famous for them. One is B. Stat and other is B. Math. You have mentioned that you have subjects physics, chemistry and mathematics. You cannot get direct admission there for any course. You need to give the entrance exam held by them. If you qualify in the exam then you will be called for an interview and if you crack the interview then only you can get admission. Moreover you should have a good score in boards also. The entrance exam will consist of only maths. If you want to ask anything else you can comment.
Please upvote if found helpful.
Thank you.