The examination for BSTAT is completed on 18th July,2021. So for year the first phase examination i.e., the written test is complete. Now the second phase will be on Interview sessions.

Thus you have to fill the form again in next year and you have to keep an eye on ISI's website. The website is stated below:

https://www.isical.ac.in/~admission/

I hope this answer helps. All the very best for your future endeavors!