To add BANKNIFTY or any other option contracts
For example - If you want to add Banknifty's September Call options, type "BANKNIFTY 30400 CALL 09 SEP" in the search box. Similarly to add Nifty's September Put options, type "NIFTY 14150 PUT 09 SEP" in the search box.
Login to the Kotak Stock Trading
Go to the watchlist you want to add the BANKNIFTY Contract to
Once you see the BANKNIFTY Contract in the Search result
Click on the plus icon on the right hand side of the BANKNIFTY Contract