To trade weekly Nifty option contracts, simply add the required contract to your watchlist  by typing in "Nifty" followed by the date of expiry for e.g., "15feb" followed by the strike price say " 21700" followed by the option type "CE" or "PE".  An additional balloon will appear which will say which week the contract belongs to, such as "W1", "W2" or "W3" and then you can press on the add button to add it to the watchlist. After adding the same to the watchlist the same balloon appears after the date of expiry for clients to easily identify the same as weekly contracts.