Hii Namrata Maurya..
Yes you need to upload the caste certificate at the time of application form without you will not get the benefits from that. And you will be considered as a general category student so before applying list all things what you need and then start the application form filling. If you are not finding any option for that they might have updated and they will check at the counselling time. So don't worry.

If you still need a good confirmation contact nift-+91-11-26542000 

Hope this helps you. All the best.