Since you are a student of chhatisgarh so it us most likely that your centre will be in some school of chhattisgarh .The examination centre will be available on the admit card for NTSE exam .In some states the whole application process is online so you have to fill the application form online and submit it there .In some states you will have to take the application form from the school or from school liaison officer .Check this article to know more

https://school.careers360.com/exams/ntse